Irish, you're doing a great job. I know it's a very hard thing, to walk the line between encouraging reconciliation between your kids and their parent, versus supporting your kids and validating their very real, justified feelings.
You're doing well with it. The only thing I would add is that your WAW, more than most, shows some clear signs of mental illness. Perhaps emphasize this to the girls, not to make them have contact, but to help them understand that this has nothing to do with them, she is sick.
Then keep doing what you're doing - making sure your girls have a great childhood and don't miss out on things because of her absence. You get a gold star!