I agree with the post above. I mean, what were the husband and the new girl thinking? That they could just do this without anyone noticing and carry on as usual?
I don't want to judge or anything, but I must say I definitely feel for the ex-wife. It's not a pleasant situation to be in already, and by not relocating you're putting yourself in a more akward situation.

And yes, extra measures should be taken. If you are easily seduced by someone else and will break up with your wife to be with him/her, then maybe (just maybe) being a dance instructor is not for you.