The hints are definitely there that if we don't help she might end up as the hooker people suspected her to be.
Just a small correction, for all the asshole that he is, i don't remember Ethan saying she should fuck them, he says flirt (which i interpreted as merely act happy and playful) rather than fuck them.
Right before he tries to rape her
.
I'm red blooded male and i was frustrated when she backed out of it in that scene.
But soon i understood that it was suppoused to illustrate how that one sexual experience has left her scarred and traumatized to this day.
And yeah she gets triple the flack of everyone else... it's curious people just don't avoid her if they despise her so much...
My guess is(in addition to prominence) people have a hard time changing their minds, so when initial introduction was "the bitch that friendzoned us" people are gonna keep finding ways to hate her, if it gets proven incorrect.