Jenny is a cute and beautiful 7-turned-8-year-old girl with blue eyes and short red hair that she mostly wears in a half updo. She appears in four different outfits throughout the film. She is first seen wearing a tartan blue and white school uniform, a blue jumper, a blue tartan skirt, light blue ankle-length socks, and black and white saddle shoes. Then, she wears her casual outfit consisting of a sleeved sky blue turtleneck. She also wears a skirt with a periwinkle belt, periwinkle tights combined with white socks, and gray velcro sneakers with a turquoise trim. On her birthday, she wears a red dress, head tie, white ankle-length socks, and black flat Mary Jane shoes.
At first, Jenny appears lonely because of her parents being away, but gains happiness as she spends time with Oliver after adopting him. After learning that he had been "catnapped", she is visibly worried and upset. She is even willing to do whatever it takes to get him back. She is kind, polite, gentle, good-hearted, nice, caring, generous, and friendly.
Jenny first appears a quarter of the way in the film with her family's butler, Winston, after her parents have left New York for business in Europe. In a limousine, she reads a letter from her mother, saying that she and her father left Paris for a conference in Rome. After reading it, she becomes disappointed when she learns that they won't make it home in time for her birthday; despite Winston's efforts to comfort and make her feel better.
Then, in one of the mishaps performed by Oliver, he ends up in her mansion, preferring it to his former life on the streets with Fagin and his dogs. Winston is against the idea of Jenny adopting Oliver for the reason that they have a dog; a champion pedigree poodle named Georgette, Winston was left responsible for Jenny by her parents, and they have to wait for her parents' approval. In the kitchen, Oliver has a special meal prepared by Jenny, who made a mess while doing so, which annoys Winston a bit. Then, she talks to her parents on the phone, after Winston answered first; assuring everything is fine, about their decision about whether to keep Oliver or not. She comes in afterwards and tells Georgette, who unfortunately met Oliver beforehand, that her parents have approved about her decision of keeping him and that they're going to be "the best of friends."
Over time, Jenny bonds with Oliver while practicing piano. As she begins to do so, after being reminded by Winston, Oliver somewhat helps her by playing a discordant note. Then she sings "Good Company" while playing the piano with him.
Later, they spend the rest of most of their fun of the day at Central Park: riding in a small boat in the lake, playing with fences, greeting people they pass by (with a curtsy from Jenny and a bow from Oliver, respectively), eating strawberry ice cream, riding in a carriage, and finally buying Oliver things with his name on them in a shop, including his bowl and finally of course, his new blue collar with a golden name tag with his name and address on it of his new home with Jenny on Fifth Avenue. He is so happy and excited that he jumps on Jenny and licks her as his way of showing his gratitude and that he loves her very much.
At night, as Jenny is getting ready for bed while singing a few words from "Good Company," Oliver jumps in as well to sleep with her, snuggles his nose with hers as he is picked up, tucked in, and told "Good night, Oliver" as Winston turns off the lights and closes the door with a warm smile on his face.
The next day, while Jenny is at school, Oliver is "rescued" by his dog friends who take him back to Fagin's barge. Fagin, seeing his golden name tag, notices that the address is Fifth Avenue. He plots to ransom him to get the money he needs to pay back his evil boss, Sykes, unaware that Jenny herself is the "wealthy cat owner".
When Jenny returns home from school and calls for Oliver, she can't find him anywhere, even with Georgette's "help." She finds Fagin's (unknown to her) ransom note along with his drawn map for their rendezvous in the mail slot. She gets worried about Oliver and resolves to get him back, much to Georgette's dismay.
At night, with Georgette, Jenny follows the confusing directions on Fagin's map and believes that they are lost, when in reality, they have reached their destination. After meeting Fagin, she tells him about how Oliver was ransomed - not knowing that Fagin himself is the kidnapper - and shows him her piggy bank, which she brought in order to get him back. After their small conversation, and feeling guilty after seeing Jenny and Oliver crying and sad, Fagin follows his good heart, gives up the ransom, and returns Oliver, whom he pretended to find in a box, to Jenny. However, Sykes, along with his two Dobermans, Roscoe and DeSoto, had been watching the whole thing in his car. He then shows up, tosses Oliver out the window, kidnaps Jenny in order to ransom her to her wealthy parents, and tells a shocked Fagin to keep his mouth shut and consider their account closed.
With the help of Oliver and his friends, at Sykes' warehouse, Jenny is rescued, while their enemies are distracted, with the help of a crane operated by one of Tito's electrical specialties. When their enemies return and Sykes destroys the crane's controls, Jenny and her friends are seen falling and landing on a long slide.
At the end of the slide, their enemies have them cornered, but before Sykes can snap his fingers to order his dogs to attack, they hear a honking noise, and bursting in through the windows, it is revealed to be Fagin on his scooter, coming to the rescue. Jenny and the gang hop in and flee. They're able to outrun the Dobermans until Sykes catches up with them in his car. Fagin, having no choice, drives his friends into a subway station, but Sykes, driving like a madman, is still able to follow them. In a tunnel, with Sykes still in pursuit, his car collides with Fagin's scooter, causing Jenny to fall off and end up on Sykes' hood. When Sykes tries to grab her, Oliver saves her by biting Sykes' hand, but then is tossed at the back seat with his two evil dogs. Then, Dodger saves Oliver by fighting off Roscoe and Oliver saves Dodger by fighting off DeSoto; killing them both in the process with the help of the subway's third rail and the friction between Sykes' ruined car tires and the tracks. On the Brooklyn Bridge, Jenny calls for help from Fagin and he comes to her aid while Einstein helps him out; leaving Tito in charge of his scooter. Unfortunately, Sykes grabs Jenny by the leg and tries to pull her back in, before Oliver and Dodger jump on him and fight him off, giving Jenny the chance to jump into Fagin's scooter.
In front of them, a train is coming their way. Tito is capable of saving everyone by jumping on one of the bridge's cables and driving them to the top, but Oliver and Dodger are still in the car, fighting Sykes. Sykes throws them out until he notices the train heading his way which then hits his car and kills him, thus sending them both into the East River.
When the rest of the company drive back down, Jenny runs to search for Oliver, only to find a sad Dodger approaching and holding him, who is "thought to be dead". At first, everyone thinks Oliver is dead but when Jenny hears a soft meow from him, she quickly realizes that he is alive and everyone is rejoiced, except Georgette, who is still in great shock from the chase. Then, Dodger and the gang are accepted as Jenny's new best friends.
The next day, Oliver and the gang are celebrating Jenny's birthday (eight candles on her cake suggests that she is seven prior to this scene), giving her birthday gifts while she thanks them for the gifts as reminded by Winston when it's time for her friends to go, and she gets to keep Oliver, as her parents already said that she could.
Jenny is last seen saying good-bye to Fagin and his dogs. As they are driving back home, Jenny is seen along with Oliver and Winston saying good-bye to them and watching them as they head back to the barge, while singing "Why Should I Worry".
Jenny made numerous appearances at the parks in the years following the film's release.
- Jenny is similar to Penny from The Rescuers. In fact, an early idea was for Penny to be in Jenny's role. Also, Jenny rhymes with Penny. They live in New York and are kidnapped by the main antagonist (Jenny, Bill Sykes; Penny, Madame Medusa) who have pets that look alike (in Jenny's case, Roscoe and DeSoto; in Penny's case, Brutus and Nero), but get rescued by animals (Jenny: Oliver, Dodger and his gang/Penny: Bernard, Miss Bianca, Ellie Mae, and the swamp folks). Coincidentally, they share the same animator, Glen Keane.
- According to one of Roscoe and DeSoto's pictures, the calendar next to Roscoe reads April 21, 1988, thus, Thursday, the day Oliver met Dodger. The next day, Friday, would be the day Jenny adopted Oliver, but the next day, Saturday, would be the day Oliver was "rescued" by the gang while Jenny was at school and the day after, Sunday, would be the day of Jenny's birthday so therefore, we can conclude that the day Oliver met Dodger was actually Wednesday April 20, 1988/Thursday, the day Jenny adopted Oliver/Friday, the day Oliver was "rescued" by the gang/Saturday, the day of Jenny's birthday. Thus, Jenny was actually born on Wednesday, April 23, 1980.
- Despite her birthday being April 23 in the film, in the Disneystrology book, it is listed as April 27.
- When Georgette "helps" Jenny find Oliver when she can't find him, she tries to look for him in a fish bowl with a goldfish inside; suggesting that Oliver and Georgette aren't the only pets Jenny has living in her home.
- During the chase, where Jenny is hanging onto the hood ornament on Sykes' car, she yells Fagin's name for help. Slightly later, Fagin yells for her to jump. They never introduced themselves earlier in the film, yet know each other's names.
- The chair that Jenny is tied to disappears as she falls off the hook and goes down the slide.
- During Good Company, Jenny's house number is 1125 ("1125 5th Ave." as seen on Oliver's new tag). Right after the song, as she leaves for school, it is now 140 (as seen above the front door). Thirty seconds later, when Winston answers the door, it is 1125 again. In some shots, it disappears altogether.
- In shots of the front of Jenny's house, there appears to be no mail slot, nor a place for a one. Later in the film, Fagin's note is placed in one which can be seen from an interior shot.