Yes . Self care is a priority and if you need to delete her messages to help not dwell on them, that is a good action.
You are right in your assessment of her, but that is only the part that is missing. Focus on the good points. 1 she wants to reconnect with your girls. 2 she wants you on her team. (This is a debatable topic but for now consider it as positive) 3 she admitted she was wrong. 4 she illuded to putting girls before current bf 5 she is contacting you a lot and apparently hidding if from bf 6 she wants you to be happy. 7 she is in therapy to help her move forward. 8 om, moving out etc have not made her happy. 9 she realises your M was good and she was wrong to say otherwise 10 she acknowledges how good a dad you are. 11 she realised she has still a void and isn't trying to artificially fill it.
That is just off the top of my head. There are surely more. I am not asking you to do anything different. Continue as you are but I think it would do you better not to dwell on what is missing and appreciate/acknowledge what is positive. You are right to be cautious. Definitely.
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