I'm at work and don't have a lot of time to post...but I'd encourage you to read up on affairs. My favorite books were Torn Asunder, Not Just Friends, and Tough Love for Marriages.
I've felt increasingly better as I've detached and taken a stand that I won't and don't deserve to put up with my H's affair. I've also been very happy that I filed for divorce back in March and started the clock ticking on that process. My H just moved out last weekend (almost a year into his A) and I felt a huge sense of relief.
You know what you can live with and what you are sacrificing by doing so. My realistic attitude is that while she's in the affair...she is so selfish and in her own world that I'm not sure that anything you do matters. (although I do think DB-ing for awhile is effective and may ultimately show them what they've lost). My H says I've been "fantastic" through his affiar...I don't really take that as a compliment.
I frankly wish I'd reacted harsher sooner...H was "mean" for awhile as I've pushed him off his fence...but he's actually been nicer and more respectful recently than ever before.
Just my two cents...some of the people on this board have an unbelievable patience for hanging around with a cheating spouse. I know I couldn't have done it if my H had been having an affair here locally. I also think if you read Tough Love...you'll see James Dobson's argument for how not tolerating the affair is ultimately more powerful and effective.
You deserve better.
M 44, H 46 D11, D9, D5 Married 12 years PA confirmed 9/2011 I filed 3/2012 H moved out 7/2012