If you feel this is pushing her away, what is your alternative.....that does not break your own boundaries?
Again, this is still your guilt working overtime. She has done a number on you! Plus, you are not detached enough or you would not get stuck over these issues. The next time she shoots one of her texts saying to call her or that she needs to talk to you, text her back right then and tell her that you are reminding her of your boundary about contacts and if she has some emergency, she needs to text it or leave a VM. Then you will determine if you need to respond.
You are beating yourself up over something that should not consume this much attention. And forget what she said about being sorry for ruining lives. She's done this before, then turn around and cut you to ribbons. Ignore it, HP. She is a manipulator! She will pull tricks out of her bag to get you back to where you were when she was in charge.
Right now, this about her wanting to be in control. It is not about her wanting to reconcile the M. She is not going to give up that control easily, but she must give it up in order to respect you. As long as she was sleeping with OM while you kept S11 at home, she was in control and had no respect for you. Now she feels very much out of control and she will use whatever means necessary to regain it.
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!