Your girlfriend says she's pregnant and you ae not the father

I think I would have had to end it with this girl. If she cheated on him then she more than likely will again. If she isn't happy enough with him to stay faithful then even if she says she is sorry and it will never happen again I believe it will eventually. I think it is very rare when a person who cheats stays in the relationship and stays faithful forever. I would for sure break up with this person if it was me.