Late to the discussion, but the fact that she actively sought to have an affair with anonymous sex partners through Ashley Madison seems an unambiguous act of betrayal. It's not as though she just innocently met someone and feelings took over. She basically went online to search through a bunch of strangers, found someone (who happens to be well off financially) and said, "Take me!" She did this not just once or twice, but repeatedly over the course of 6 months.
It's not my place to speculate here, but I will anyway because I've seen this before with couples I've known... From a distance, it simply looks as though she wanted an end to her financial challenges, wanted some kind of do-over in marriage and life because she wasn't happy for one reason or another, and probably wanted to be with a man who was richer that the OP. She's probably in her early-to-mid 30s and feels as though she still has a time window to take a shot and see if she can attract a man whom she likes. So she tested the waters for 6 months to see if she can pull it off. She's conflicted, but not nearly enough to stop her from pursuing this for 6 months. She knows she's giving the OP almost no choice but to leave her, and this is probably the outcome she wants, presuming she can "find someone better or more to her liking." To do this in a situation where there are kids involved makes it all more deplorable.
The above may sound harsh, but I've seen it before. (FWIW, this is a real trend with Russian women whom I wouldn't touch with a 10-ft pole. They marry for convenience, then dump, then remarry when it suits them. The problem is ultimately that they marry too casually the first time, and likely the second time as well.) The woman is comparing her life with the OP to a vision in her head of how she'd like things to be, rather than being committed to adapt to and make use of the way things are.
That, or it's simply a case of unbridled sex addiction, but I'm guessing that's not really what's going on. It sounds like she wants out and has admitted as much.
</said too much>