OK, I thought you had talked to a lawyer and he had told you that there was a possible criminal case you could file for infidleity or something like that.. maybe I read it wrong...
You are right, the three months may help, IF she follows through... but the fact that she ran out of the house to talk to him as soon as she negotiated the deal is a pretty strong sign that she's not going to follow through.
I would just look for any good reason to stand firm in three months... and have her out of the home.. I wager it won't even take that long...
