HP.. whenever I've complained about my WAH not keeping to our schedule, it was suggested that I approach it like a problem we need to solve together. What does she suggest? That you keep S11 all the time? Ok, perhaps you can understand that her living situation is less than ideal... can she offer a suggestion to give you some time to yourself, too?
It seems like when your approach is open and kind, she responds in the same way...and is very sensitive to not feeling listened to (hmmm...). So, listen, validate. Then, don't use "but"...use "and" you have commitments and needs for time too. Ask for her help (in an open, problem-solving way).
I think you'll be surprised at how she responds. I think she seems to feel shut down by you, and perhaps that is a trigger.