What is Sara's greatest power?

Sara's greatest power can be found in her generosity, kindness, and ability to put people at ease.

"If I WAS a princess—a REAL princess," she murmured, "I could scatter largess to the populace. But even if I am only a pretend princess, I can invent little things to do for people. Things like this. She was just as happy as if it was largess. I'll pretend that to do things people like is scattering largess. I've scattered largess."