Amy is the oldest child of Wayne and Diane Szalinski. She does not share the scientific interests of Wayne and her middle brother, Nick, but is more focused on typical teenage interests. She is shown to care about Nick, though his antics sometimes annoy her. She tends to be more cautious, but usually goes along when she is outvoted. Early on in the first film, she was shown to be more concerned with popularity, but eventually starts a relationship with Russ Thompson, Jr., her next-door neighbor.
When next-door neighbor Ron Thompson hits a baseball through the Szalinskis' attic window, it, unbeknownst to anyone, activates Wayne's shrinking machine. Russ Jr. forces him to go over and apologize; in response, Amy sends Nick upstairs to help him retrieve the ball and clean up the broken glass. When neither returns, Amy and Russ Jr. go up after them, only to be shrunk by the machine.
Wayne returns home, but the kids are unable to make themselves be known. After destroying the machine in a moment of anger, he sweeps up the mess, and the kids, into a garbage bag, which is then set in the backyard. Amy is the most reluctant to leave their position but eventually follows in an attempt to make it back to the house. The boys attempt to climb a flower to see how far the house is, but Russ Jr. and Nick are separated from Amy and Ron when a bee lands on it and takes them on a wild ride around the backyard. Ron initially refuses to go on, believing the entire thing to be a dream, though Amy boxes his ears to get him to do so.
Unfortunately, Wayne, having realized what happened, accidentally turns on the sprinkler while searching for the kids. Amy and Ron are forced to run for cover from the giant drops of water. Amy becomes distracted after seeing Nick and Russ Jr. nearby and is knocked into a muddy puddle. She nearly drowns but is saved by Russ Jr., who performs CPR on her. They then continue on.
Later on, the kids come face to face with a large oatmeal cream cookie, which they begin eating hungrily. They are scared away by an ant, though the boys make plans to try to capture him to use as transportation. When their methods fail, Amy is able to bribe him with a piece of the cookie. Nicknaming him Antie, they use him to travel faster.
The kids choose to spend the night in one of Nick's Legos. Amy and Russ Jr. have a discussion, where he admits that he liked her but was too intimidated to say so. She also learns of his difficult relationship with his father, Russ Thompson, Sr.. They share a kiss but are interrupted when a scorpion attacks. It is eventually defeated, but Antie dies as a result.
The next morning, the kids are once again attempting to get to the house, but are forced to contend with a lawnmower when Nick's friend, Tommy Pervis, comes to mow the yard. They take refuge in an earthworm tunnel but Tommy stops the mower over it. Amy is left as the last person attempting to hang on to a root, but she loses her grip. Luckily, they land unharmed, though they briefly panic when they realize that they have missed being seen by Wayne and Diane again.
At that point, the Szalinskis' dog, Quark, shows up. The kids manage to ride him into the house, but Nick falls into a bowl of cereal Wayne is eating. Thankfully Wayne notices him and the others, but not before nearly devouring him. Gathering Russ Sr. and his wife, Mae, Wayne attempts to figure out how to return the kids to normal size. They are able to use charades to reveal the baseball as the culprit (it weakened the laser). After testing the idea on Russ Sr., Wayne returns the kids to normal size, who happily reunite with their respective parents.
The Szalinskis and Thompsons come together for Thanksgiving dinner, where it is revealed that Amy and Russ Jr. are dating.
Amy only appears at the beginning of the film, where she is shown going away to college. It is also unknown about her relationship status with Russ Jr..
A younger Amy appears in the TV show. Her depiction is generally similar to the films. She sometimes either makes use or is the victim of Wayne's inventions, though the problems are usually reversed by the end.