My friend is pregnant and her bf might not be the father

Niall and Sho got such a tough dilemma this morning from a girl"In June myself and my girls group went to Spain for a long weekend. It was mad as you would expect. One of my friends had a two night thing with this guy from Wales. She has a boyfriend of two years so we were all a bit like 'that's bad' but just said nothing. She said it was holiday fun and nothing else. Fast forward to now and she is pregnant and confessed to me at the weekend that there's a strong possibility that the father is the guy from Wales and not her boyfriend. But she said he will never know cos he's across the water so it's all good and her boyfriend is so excited. "What should she do? Huge reaction to this