Well, as anonymous pointed out, she's never on screen long enough to be pushed around. She's usually there for a one trick pony gag, then forgotten about.
But see, off camera, she's being told by her mom to run to the store for her because they forgot the tofu, again. Or the student body president is asking her to do a bunch of makeup work that he should be doing instead. Or she's helping that old coach soothe his hemroids by applying the cream with her tongue.
Seriously, the girl just can't / wont say no. The symptoms are all there.