Ugh, you have gone through a lot this year! It's too bad your sisters don't understand or have more compassion for your situation. I can see why you would want to take a break from contact with either of them. You are making the best choices and decisions you can in these circumstances.
I'm struggling with isolation during Covid. I think of myself as an introvert and am somewhat surprised at how lousy it is to just not see anyone. It was different when it was my own choice!