Dolores first appears serving a few barflies at the Pacific Electric Red Car Trolley Terminal Bar, with Eddie being one of them, though she stops him from taking a sip of his drink when she reminds him that her boss checks the books on Fridays, and if she doesn't get back the money she loaned Eddie before her boss notices the difference, she could lose her job. Eddie shows her he already has half of it, but she's still livid to know where the rest is. Then he asks about borrowing her camera as his is in the shop, but she scornfully believes Eddie's is in the pawn shop, until he convinces her that he needs it if she wants the other half of what he owes her to save her job. Convinced and calming down, she hands it over, mentioning the roll inside hasn't been developed since their trip to Catalina Island, so there should still be a few exposures left for Eddie to use for his assignment. She notices when he loses his composure after one of the barflies, Angelo, makes fun of him, believing he works for toons. She is quick to garner the barflies' sympathy for him once she reveals the truth behind his hatred of toons to them, explaining that his brother, Teddy, was killed by one by having a piano dropped on his head. She apparently cares for him and even helps him when the latter explains about Judge Doom and the Toon Patrol, who are all after Roger Rabbit because he supposedly murdered Marvin Acme. She also seems to know about his will, as she warns Eddie of how Cloverleaf Industries had placed the highest bid for Toontown and will acquire it at midnight if Acme's will fails to show up by then when Toontown will be put up on the auction block.
She plays a larger part in the film's climax, where she saves Eddie from almost being killed by Judge Doom and the Toon Patrol when they come for Roger at the bar by providing a drink that causes him to erupt like a high-pitched steam whistle so Eddie could fight off the Toon Patrol and rescue him. She armed herself with a bat in case things escalate further. For her part in the bar fight, she presumably got fired as a result, which was fine for her because she admits, "Stuffing olives for a living wasn't for me anyway." Following the climactic battle at the Acme Factory that saw Judge Doom's death, she arrives with Benny the Cab, Lt. Santino, and the LAPD, where Eddie proves Roger was innocent of murdering Acme, while Doom was guilty of murdering him, R.K. Maroon, and Teddy, along with the attempted murder of everyone in Toontown.