More mental health musings

My sister and I have a very weak thread of communication right now. I am concerned for her. I know she has some mental health issues. There is enough distance physically between us that I can not with four children easily schlep up to see her. And frankly I don't know her actual address, only the town she is living in. She is presently living with a friend while she gets herself and her life back together. I email her a couple times a week. And I agonize over what to say. Is it hurtful to talk about our family and what we are doing together? Is it reassuring to have someone write the same way they have always written to her, or does it seem insensitive to whatever it is that she is going through right now? Is it intrusive to keep asking "hey, how are you doing?" "sis, we are thinking about you and want to know how things are with you?" or even "what are the kids up to?" I never hear the latter and I worry for them. I know she has work to do on her own issues; I wonder if there is time and energy for theirs. But I can't ask that; I know that for sure. So I wander through this very blindly with no real idea if I am helping or harming and I hate that.