If a friend of yours (not at your uni/whatever) just broke up with their ex (and it was a bad breakup and your friend dumped him/her), and you know the ex and you used to say "hi" to him/her every time you walk past him/her (because he/she goes to your uni), do you still continue saying "hi" knowing that your friend and the person don't go out, or do you pretend they don't exist? It's a bit of a weird situation.