Sure! Here's the requested content in spun format with synonyms:
Cara is crazy about Finn and Frank.
Cassandra Finn, and Ferb.
Finn Cara, and Ferb.
Cassandra being with Phineas and Frank.
Phineas Candy,
and also Ferb.
Cathy shares a bond with both Finn and Foster.
I hope you find these variations helpful!