She lives in Danville USA, across the street from her two best friends, Phineas Flynn and Ferb Fletcher on Maple Drive. She has a crush on Phineas and is always eager to help out in their summer ideas when necessary. Although Phineas is shown to be unaware of her feelings, he cares deeply for her, and it can be assumed that he has the same feelings for her.
- Isabella will star in The FT Squad's Adventures With Phineas and Ferb, where she's often accompanied by Kyle Larman when she says hello to Phineas and Ferb.
- Isabella will guest star in The FT Squad Rides on the Magic School Bus, The FT Squad Goes to Jurassic Park and The FT Squad Goes to Monsters Inc.
- Isabella acts like a sister to Kyle Larman and cares deeply for his welfare. Kyle knows about Isabella's crush on Phineas and does what he can to help Isabella get Phineas' attention. Kyle, more often than not, goes wherever Isabella goes, especially if she's going to see Phineas. Isabella doesn't mind Kyle at all and is always willing to help him when he needs it and won't hesitate to comfort him if he's sad or scared. Kyle has always seen Isabella like a sister figure and they love having fun together and helping Phineas with his ideas and activities.
- Isabella is the owner of Barney the Dinosaur, and helps hold the key to his world of imagination. She, along with Phineas and Ferb, will also become members of Barney's Backyard Gang, and Isabella will also join the Hey Girls.