First, my condolences on the loss of your sister in law. It must be very difficult to grieve the loss given the circumstances.

As for your MIL, you are obviously a very kind and loving person to even want to support her in her grief despite how she has treated you. I have a few suggestions that may help you cope with this situation.

My first thought is to have conversations with your father in law instead. When I used this communication tactic, I gained quite a bit of knowledge that enabled me to better navigate the other relationship. It turned out that my MIL was feeling like she didn't have a relationship with her son and blamed me and our kids for taking up all his free time.

In your situation, I would ask your husband to take his parents out instead of coming to your house for a visit. Have him take your daughter to the park with Grandma and Grandpa for a bit. Then meet up for pizza or something for dinner. Sometimes an audience of strangers is enough to keep the worst criticisms unsaid.

Another alternative is to run your own errands or take a walk when they come over. Let your husband deal with any criticism she may offer about your home and family. If they ask why you weren't around for their visit, tell them you weren't feeling well but you wanted to support them in getting out of the house. (anxiety and stress makes you feel unwell, right?) I don't recommend avoidance often, but in a pinch when you really can't deal with it, it's an option.

Relationships with in laws can be challenging. I hope you and your family find a way to manage it that works. And again I'm sorry for the loss you are all dealing with.