Your story doesn't make much sense to me. You seem to be talking about a woman who has done something sexual with other people--and now she gives you sex, but now that you've had sex with her, you're unhappy with her giving away sex? That's confusing to me.

Maybe the best thing would be to not have sex with someone unless you resolve in your own mind where your receiving sex fits in with other people receiving sex. I hope that makes sense.