When she first met him.
Yeah she was a bitch to him, he liked her and she was being a real snot to him.
He was a drunk, entitled rich kid who was very disruptive... What'd ya expect?
I think she didn't like him at first because like she said, just because his dad is rich, Billy got to do it again. But later on, she started to like him, when she saw how good he was with the other kids.