Isabella is the neighbor and a friend of Phineas and Ferb. Isabella has an obvious crush on Phineas; however, she doesn't tell him. She's the leader of Fireside Girls Troop 46231, and often volunteers to help in Big Ideas, usually with her troop being involved.
On Sora's TeamEdit
She's always doing a good job a keeping everyone focused and helps in assisstance with other members on Sora's team with the other Fireside girls.