I imagine well that you have many feelings at this time some probably conflicting. You are probably right not to attend. I tend to think of death differently since I lost my dad and where possible I extend sympathy to those in bereavement.
You reached out to XW which I also agree was right thing to do. As job warned your XW is likely to be even more messed up in the aftermath and that is best to leave her deal with it.
I am sure her words sing as the same old woe is me without my daughters. One day the penny will drop for her that her actions inevitably lead to that. Until then try to be empathetic and realise that it really must be tough without them. Imagine if it was your dad and you hadn't your daughters.
Unfortunately it is likely that she will settle further into the pity party. Expect this, but let it slide. This is a tough time for her and I doubt she will be able to rethink her viewpoint until she absorbs this death.
Your upcoming plans sound great
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