I seriously cannot tell whether it's good that the social worker is finally taking your sister's problems seriously or that it's bad happened because of a fluke.
Her mother-in-law taking her child away is bad either way.

I hesitate but will ask where her husband is.
Her husband works as a Latin teacher at a charter high school, and sometimes tutors kids after his main job. He is probably back at their home now. We spoke to her on a Facebook Messenger Video call for about an hour, ending at 5:26pm. He was not home when we got off, but she expected him back around 5:30pm. Some people from his work wanted to bring them food, so she did not need to cook dinner, but he said he still wanted her to have the table set and a drink ready when he got home.
For much of the call she seemed distracted by trying to figure out what to do with a bag of potatoes that had gotten wet (if friends were not bringing food she would have gone ahead and cooked them before they have a chance to go bad) and then trying to find the missing USB receiver for her wireless mouse, which she was afraid one of their 3 cats might try to eat. She was also trying to do laundry while we talked, and in the previous call was trying to catch a spider.
My sister said she has no idea who called the Division of Family and Child Services or why, and wishes they had not gotten involved. She did not understand why the lady was asking the sort of questions she asked, and her mother-in-law did not know how to answer them either. She did not say what any of the questions were though, and gave no hint that they related to her husband. She seemed to think it all had to do with her having been institutionalized and having just started a new antipsychotic medicine to help her sleep.
It could be my fault for taking the advice of people here and sharing my concerns about how her husband spoke to her with a social worker at the institution.
---
Mom's physical therapist still never showed up today. I mentioned this to the occupational therapist who called to make an appointment for tomorrow, who said she would bring it up with their boss.
Mom was really upset about having had to stay dressed all day for a therapist who never came and is afraid tomorrow will be just the same. She was crying about it. I honestly think her mood might be more related to having heard about her granddaughter being taken away, but with the neurological damage from the stroke she did not seem able to concentrate on that fact for long enough to consciously realize that it was what was really bothering her.