This sounds like it could be a very positive development. It's way too early to let your guard down. But, I think you should still remain open to working on your M (which I assume you are).
I would definitely make the appointment with the C she mentions. The fact she's willing to go and work on your M is a good thing. I would kill for that.
On the things you know you have done to hurt her, you need to acknowledge and own these. Then you need to change. She is telling you her concern - that your changes may not last - and this is VERY common for a WAS to have those concerns b/c they have seen us act otherwise for a long time. That will only change with consistent ACTION on your part plus time. So, keep up your changes.
On the possible A, is it a dealbreaker for you? If it is true, are you done or could you forgive her and help repair your M? Unless it's a dealbreaker, I don't know that you should push on that issue right now. That will come out in C. I DO think you should keep your eyes open, and maintain a boundary of no contact with OM - NONE. And she needs to be willing to give you access to her information/cell phone, etc. to prove it. If she asks you why you need that, calmly explain that, just like her, you are working on things that bother you - and you have to be able to trust her. Right now, based on HER actions, you are having a hard time trusting her in that area. You want to rebuild that trust, but it going to take time and work on BOTH your parts.
For now, I would make the C appointment and work on rebuilding your friendship. Laughter is wonderful for that. Keep the conversations light and upbeat. Maintain a positive mental attitude. But, no desperation, no pleading, no begging, no anger and no resentment. In short, no pursuit. That doesn't mean no rebuilding the friendship.
