Isabelle Garcio-Shapira

Isabelle Garcio-Shapira is essentially the opposite of Isabella Garcia-Shapiro.

Phineas Flynn
Likes Phineas. Would like to marry him someday.

Isabella Garcia-Shapiro
Isabelle humiliates Isabella the first time they meet, and Isabelle proceeds to flirt with Phineas in front of Isabella, causing Isabella to dislike Isabelle.

Ferb Fletcher
Would like to marry Ferb someday after changing her mind about Phineas.