She is doing all the contacting not him. That email was from her to him. He has not responded. Nor has he responded to the other ones she has sent.
I'm not the expert on these things, but if you believe that he's really not all that interested in her, you can use that to set a boundary.
You could confront her, say "If you want to be with him, go be with him" and help her pack her things. If he's really having second thoughts, her showing up on his doorstep with hat in hand could be enough to make him break it off for good.
What you do from there is up to you.
(If you do this, be prepared for her to go and him to take her in. You don't bluff with this kind of thing.)
Me: 44, Wife: 39 M: 17 years T: 20 years Bomb on 08/25/09 1/13/10: MC started 1/28/10, 2/8/10: More bombs 8/28/10: Wife moved out No talk of D, no movement