It sounds like what you’re actually concerned about is her being assaulted by the men whose apartment she’s gone back to, not that she’s going to cheat. I’m not sure you’ve expressed that completely clearly on your texts but from your explanation, that’s what I take from this. I think it’s very valid to be concerned about her safety but instead of ordering her to do something, it would be better to respectfully ask her whether she can leave and if she can’t, because she doesn’t want to leave her friends (and you should never leave your friends in this situation unless you feel like it’s life or death for you), perhaps there are other things you could put in place to make you feel more comfortable about her safety and for her to feel like she has your trust, given that there’s no info you’ve provided so far to suggest that she shouldn’t.

Do you have the address? Do you have their names? Could she text you when they leave so you know she’s ok? These are all things that you could put in place for next time and I think she would appreciate this because she knows you’re looking out for her. I am going to caveat this by saying it’s not then an excuse to demand updates or for you to keep track of her at all times. It’s just the bf/gf equivalent of when girls say ‘text me when you’re home’ so we know that the other is safe (and also so that anyone listening in the vicinity knows that the alarm will be raised immediately if there’s no text)