Getting to this point is whatever. All these guys are the epitome of hardcore pimps so of course they have never done anything they didn't want to do to please a woman.
Me, you and all the ordinary non-coli posters definitely have and will continue to - especially if she's young and fit.
From here, it's a bit delicate but you definitely have to dead this shyt. The only reason to stop is because it's bothering you.
Basically there's a 75% chance that she will try to flex on you by breaking up with you to feel that she 'won', but you have to be fully prepared to cold walk away if you can't have your way with this.
When you go in, you gotta go in not giving a f*** about the outcome - other than the cessation of this obligation. Like I said: most likely she gonna try to flex and the only way to overcome that is to be stone cold like she's already gone. Then the 'win' of her breaking up with you is nullified and it's almost like you are dumping her since you won't be willing to budge.
Just be assertive. Be honest and direct. Be pleasant and calm, too. If it comes to you having to step off, do it with pride and force without looking back. She might hit you up in a few days if you walk off strong enough.
If you end up bytching with her about it then it will be a definite L. Don't discuss it any further than saying what you have to say, listening to her retort, then going back and underlining your position.