Ok back to Bella's question
If this was a mate of mine I'd say wake up to yourself there are plenty of unmarried women out there. Chasing a married woman who lives interstate must be one of the most desperate things I've ever heard. In saying that some of the things you say lead me believe that this bloke is a chick, although hopefully it is not you considering what I said above.
Although the real villain here is the woman, as I can bet she has been complaining to your friend about her current husband and playing the pity card. If she is unhappy than just leave him as looking for the next best thing while still married is a dog act. Even if she does jump the fence and go with your friend 90% of the time the grass in no greener.