I like how bttrfly wanted you to consider her being sick or emotionally inapt. I personally se my W as being unwell. I believe she isn't well and her behavior towards me reflects that. This is not excuse making nor giving a free pass it helps me to think she is doing the best she can, even if that is not good enough. This enables me to respond compassionately and with empathy.
I think your W is not well. That should be the foundation where forgiveness can be fostered. Forgiveness is a choice and should not be reliant on a specific return. It is about you. It does not change the past but can help improve the future. It does not diminish the work W has ahead of her. But she is in therapy and is reaching out consistently or at least regularly.
I am sure your girls have at some stage annoyed you with some behaviour or incident. That is normal. You have not dwelled on such occurrences and have fostered a superb relationship with them. I say this to point out that W is not entirely wrong in her statement about them doing stuff that contributed. I reiterate she is wrong to blame them and only wanted to point out another perspective.
Also her trying to get them to share the blame could be considered as a misguided attempt to get on the same team as them. He and them contributed and all three can work together to rebuild a R. I do not agree with this approach and she does need to take more ownership of the R, butmaybe just maybe it was not to blame them just to blame them, but an effort to create a common link and hence starting point.
You were right to push back at her . I have mixed opinions on you replying for your girls.
You are a great dad and the girls are lucky to have you. Would you have been such a great dad or have such a close R with your daughters if your W had not left? You don't have to answer but I suspect your R with the girls was enhanced by having gone through this. A super silver lining for a big dark cloud .
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