I don't have the same experience or insight as job, but I was about to post a very similar reply.
The mention of the M not having been fake indicates her thinking is beyond just her daughters. Maybe she regrets her decisions and actions. It a a good step.
If I had discarded my family I would be wary about reaching put. It is a huge step. You cannot take it for her. Leave her decide her next move. She will get back to you. Not replying was probably your best response.
I would have been tempted to thank her for her concern but that you are confident you can manage. Inversely I would also be tempted to ask what she is asking you to help with. It is hard to know how we would react in someone else's situation. I think you handled it good.
Best wishes.
R 25 years M 14 years S11 & S13 Working on it alone since Oct 2014 M in trouble a lot earlier (~2 years) Feb 2016. 1st R chat in a yr. Next R chat Aug'17 Still together