Better advice for Michael:
I've thought about Michael's situation with his ex lover, and I arrived at a solution.
First, the girl is a partier and her intentions aren't all that honorable, so she's not that great. Michael took advantage of an easy situation, so they both got what they deserved.
I say he can either just ignore her or tell her he has a new girl, but he'll see her as a gik.
Ignoring will bring diminishing messages but no immediate resolution. The other way he's honest, can get together with her when the mood strikes, or she'll be offended and go away.
Either way he wins.