As chip says don't confront her.
Remember also you DON'T OWN HER, if she wants to go off and cheat it is HER choice, you will soon get to hear about it, and can then decide if you want the relationship or not.
Girls tend to be a LOT more faithful than boys, a bloke is a stud if he sleeps with loads of women, a girl is a slapper when she does the same with men, you have heard it before.
She will be only too excited to tell you all about it, when she gets back.
tabetha