Snow White is cheerful, but I don't think anybody was seriously hurt during the movie except for her. None of the woodland creatures or the dwarfs got injured, so being compassionate wasn't a requirement.

Belle takes her father's place, which is noble, because she loves him. I find this is selfless, not compassionate. Belle basically is really at fault for forcing Adam to fight off wolves to save her life. The fact that she bandages up his wounds later is the least she could do.... She owed him a real apology. Contrary to how everyone around here praises her, Belle really just isn't all that compassionate. Adam turns out to be the compassionate one... He gives Belle a library. When she gets lonely, he asks her what's troubling her. Adam allows Belle to see her dad via the enchanted mirror. Adam even lets Belle go home to her dad ( even though he believes this will doom him) because he loves her. Belle later inadvertently repays Adam's kindness by tipping off Gaston and his mob to the castle's whereabouts. Belle causes Adam to become so distracted, that he gets stabbed in the back during the fight for his life and home. If Belle had been more compassionate, she would have been patient enough to hold back and wait for the men's fight to be well and truly over. Belle is selfless to an extent. Beyond that, she is aloof and a snob, preoccupied with her own misery and desires.

That being said, the only really compassionate one of these three is Cinderella. She acknowledges the needs of tiny creatures. She makes clothes for mice, removes them from traps in the house, and prevents Lucifer from killing them. And Cinderella is patient enough to get all of her work done, day after dragging day...and exhibits kindness to people who treat her like dirt ( her awful stepsisters and nasty stepmother). Cinderella wins this one in my book, hands down.

Definitely

Her and Cinderella