Well, it kind of depends how much you care about the person. As Justin said, he almost asked her to marry him. Given that, it was clearly a very serious relationship, which couldn't have been lacking much, or he wouldn't have even considered this. So, even though she made a mistake, everything else must have been in order, or he wouldn't have been thinking so seriously about her. The relationship is the issue. If its just some girl you met at a bar, and you've been going out a few months and she cheats, get rid of her. But, if you've been together years, and everything else is going fine, you have to look into it more before just saying its over. The circumstances are the key! How did it happen, and why is what really matters. I don't know, I can't imagine in a serious relation just to end it so quickly. This is the biggest reason to end it, but still, you can't just say cheating equals break up and end of discussion. Maybe for some people it does, and maybe if it ever happened to me, I would feel the same way. I just think personally, i would try to work through it somehow, assuming its possible. I would say in MOST case, he or she doesn't want to work through it, or they wouldn't be cheating in the first place, but this situation doesn't sound like one of those cases.
