Raging hormones can and do make horny teenagers take such bold chances... I would expect popular boys are even bolder than most, as they have more chance of a girl actually consenting to sexual acts.

Proof?
Check the stats for teen pregnancies, its like a global epidemic

If a girl flashed a nipple at you when you were 15, I'm sure you wouldn't want it to be held over your head years later... How would you even argue the logic behind the resentment?

I say this as kindly as possible, see a therapist so you can get over yourself, the world is bigger than this bubble you're living in. Make room.

PS. It is very concerning that you have suicidal thoughts over something that has absolutely nothing to do with you, therapy seems imperative.

PPS. The only other option is to break up with her, at this rate it looks like that would be best for both of you.