Bry, to answer your last question -- of course she should have thought of you. But the fact of life is that a married person who has an affair is totally self centered; totally selfish. She/he thinks of no one but herself/himself. Cares about nothing but what she/he happens to want at that moment in time. And that is how the WS is broken. And it is what HAS to get fixed.
If she is not able to truly think at least equally about you and your needs as she does about her own, life will never be what you want it to be and what it should be. Unfortunately that will take time. Most people that are so egocentric often are also to proud and stubborn to even recognize and admit that they are egocentric. So it takes time and real work for them to get to the point of seeing and acknowledging the problem and then more time to learn how to change and become empathetic.
It truly was not about you. It was all about what she wanted for her ego and her "at the moment" whim.
I was troubled by your comment about her saying she wants to stay because you are a good guy and the history. I can tell you that I have BTDT and, at times in a more pernicious way. For a very long time after my DDay my W would periodically fall into depression, become vicious and then scream at me "I'm only staying with you because of all the money you make and the lifestyle I can lead". She would then come out of the depression and tell me that "of course I didn't mean that". So I truly get why her statement bothers you. It makes you wonder whether she is staying for love or because you appear at the moment to be the best option.
All I can offer is that you need to understand that your W is still screwed up. As much as you are reeling as a victim, she is reeling as she begins to recognize the enormity of what she has done. She is questioning everything she ever believed about herself (self worth). She is trying to understand why and how she could have done what she did. She is trying to figure out how to fix herself. And she undoubtedly is still afflicted with a lot of the "its all about me" thought process so that finding empathy for you is still a work in progress. In the midst of that, she sounds like perhaps her communication skills are probably not well honed. And so what comes out doesn't truly factor your needs in nor expresses her full feelings about you.
My W, unfortunately, still has a lot of the "all about me" in her. She has, however, learned the importance of expressing her appreciation of me and love for me and has learned how to do it in a very honest and positive way. The point here is that mine didn't get there overnight -- by a longshot. It takes a lot of time and work for them to get to that stage.
I know that newcomers to SI hate hearing the "it takes a lot of time". I wish there was one time pill we could recommend that provides instant understanding and change in a Wayward. Since there is not, all that can be offered is -- patience; time; take care of yourself; insist that she keep working hard on fixing herself.
