Your anger and frustration showed in your replies to he. Understandable but will probably not help any of ye. I believe at times we need to hit back with some home truths. That being said if you cannot reply without anger/emotion I suggest you wait 24 hours to reply. Even consider not replying.
Your W is not feeling good at the moment. That shows. She is all over the place. Accept this and leave her to it. She isn't capable of doing what it takes to reconnect with the girls YET.
I would not assume she was manipulating with regards to her contact. Her pain is making her see things differently to you. Don't forget she is also coming to terms with losing her dad. It may not be within the week but he is being treated to be comfortable not cured. I went through that a few years ago. It is tough. I'm just saying that she has a lot on her plate. Be compassionate. By that I mean feel empathy, but ultimately these are her issues to deal with. Give her space and time.
Maybe the death of her dad will have an affect on her where she re evsluates her thinking. That can be a catalyst that ends some mlc. Regardless I fear she may not be capable to reconnect with the girls before dealing with the loss of her dad.
I am glad her sister reached out to you. That was nice. I do hope the girls go to see their granddad.
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