Mavrik, your W is wayward, and she is not going to be the woman you have known all these years. Therefore, you cannot expect her to act the same as before, and more importantly, you cannot continue to deal with her and this situation as you would have in the past. You have to take a different approach.
A wayward wife is not logical, therefore you cannot reason with her. A WW is the epitome of selfishness. She will put her own desires ahead of anyone else (H, kids, family, friends, etc.) She will risk her reputation, career, friendships/relationships, even give up her kids, to be with her OM.
She will tolerate less than the lifestyle she's become accustomed to, in order to be with the OM. However, she will put her own security first. (That's where she'll use you....as her backup plan.) She will try to drain you of your last penny, charge everything she can, talk you into financing her affair (car payment, insurance, gas, phone, etc.).
All cheaters lie, as she's already proven. You cannot trust her about anything.
A WW will play the victim, justify her reasons the M didn't work out, try to turn your kids against you, and play you for the biggest sucker that ever lived (at least you'll feel that way). She will twist and turn things around to make you feel as though it's all your fault. You'll be apologizing for her A, if you aren't careful. Everyone makes mistakes in M, but nobody is forced into an affair. It was a choice.
Do not trust her female friend. That woman will tell your WW everything you say! Besides, she obviously doesn't know the mindset of a WW. Few people do understand that mindset, unless they have either experienced being a WW, or going through the hell of having one for a W.
If you are interested, I have 3 threads on the WW. Cadet has it listed in his first post to you. Also, many people have found that the 37 rules helps them get on track when first coming to terms with a stitch such as yours. I hope you'll read about detaching, b/c it is not what most folks think about detaching.
Posting as much as you can, is important.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!