I am not a proponent of dating whilst separated. I had two one night stands and like Sparks, was upset afterwards. Hollow in fact.
What I am saying is that your W has abolsutely no right at all to protest if she has gone from the marriage and even less if she herself is lying, cheating, being abusive etc.
Before doing it, ensure that you're ready.
Me: 46 W: 46 T: 23 M: 20 DS12 DD11 DS5
W left: 01/28/08 Discovered OM: 02/26/08 W back for 9 days: 04/08 W returned 05/21/08 EA/PA - 01/08-07/09 W's MLC 2008-2014 (realised this much later)