IDK about your friend cheating, but her having broken up recently is not a valid reason since women are "emotionally stronger". They might make a drama about it, but they get over this stuff quicker than guys do (in general). But I completely understand if you didn't want to make a move, because she used to be with your friend. I would never go for a friend's ex before I ask him if it's ok with him. That doesn't go for an acquaintance, though, especially if we barely see each other. You leaving town is also not a good reason since it doesn't mean that you can't spend some nice time with her. Maybe it will be great and whenever you come back into town, you will have a female friend to hang out with.