@Rusty1981133,
Quote:I don't know what to tell her
Here is a novel idea. Tell her whether or not you are ok with what she wants to do. If you are ok with it, great. If not, tell her no.
Quote: If I say no ? She will cheat.
What you are saying is that she does not love you enough to be faithful if you say no to her desire to screw your buddies. If you truly believe this, then as stated in a previous reply, you have problems.
That is up to you. If it were me, I would tell her no and let her know in very certain terms what the consequences would be if she should cheat on me. Then we would have a serious discussion about why she wants to screw someone else. But that is just me. I put a lot of stock into wedding vows.