If they want to go let them go, who are you to deny them fun? If they are the type of person who would like to sleep with someone else while on vacation, whether alcohol/drug induced 'mistake' or otherwise, then more power to them. Sure it will hurt, if they led you to believe it was a monogomaus serious relationship, but that is something that must be discussed... who is one adult to try to control another and who they sleep with, whether it be guy/girl or whatever other dichotomy... and perhaps being okay with them doing that will make them realize how awesome you truely are, for accepting them and at same time wanting a truely monogamous relationship with them. Because that is a very special thing.
Love and light
Love and light

