Husband and sister don’t get along, desperately need help

So my husband and I had a fight last night about my sister. We live in a multi generational home with my parents as well as my sister, her husband and their 3 kids. Since moving in, the relationship between my sister and husband has been very strained. We live on a farm which requires a lot of work, much of which my sister does as she doesn’t have a job. My husband mows every weekend, but every time he mows my sister points out all the ways he did it wrong and all the spots he missed. Honestly this is just the top of the iceberg. My sister is high functioning autistic and she struggles with speaking bluntly to the point of being rude. She is highly critical of almost everything, from the way we raise our children to the way the dishes are done to the way the community space in our home is used. She is used to her routines and if they are disrupted the whole house suffers. I feel very stuck because my husband is at his wits end, he feels like a child who is getting scolded and like we live under a microscope. I love my sister and feel like she has good intentions but struggles with the delivery, and I know she has a very hard time understanding social rules. What do I do? We can’t move, but I’m worried my marriage won’t make it through much more of her criticizing and disapproval. We have talked with her and she apologizes every time but nothing changes, as she says she isn’t able to realize that she’s doing it in the moment. Please help!