For what it's worth, no. It's been ages (91-98) since I was a cheerleader, but yes, that was the general culture. Cheering for, or having any remote allegiance to, a rival squad was worth hazing that would make you shiver thinking about it.
Camille probably meant that, Britney needs to either give it her all or get off the squad. If she wasn't happy cheering at her new school, most likely, she would put In the minimum amount of effort which would cause the team their chances of winning.
The problem wasn't that she still wanted to be their friend, is that she lied about her dog dying just to get out of a game, and wasn't up-front with Jesse about her boyfriend. He was hurt because he really liked her and Britney kissed him instead of mentioning her bf.