It Was Fun But Your Bestfriend....

So me and a friend were talking about her and her ex breaking up and now his bestfriend is doing the most to get with/at her. My personal opinion; if two people break up and they have no want or incentive to [ever] get back together, shouldn't really trip over who each other is see'n. The fact that it's a bestfriend does complicate things becuause chances are when the two of you hang out your ex is gonna be in the picture as well. What if the bestfriend looks way better and thats who you wanted in the first place though? [haha] What would you do?