Who is wrong?

So I was exposed to COVID last week. My therapist unknowingly had COVID that he contracted from a patient. Patient comes in Wednesday, Therapist contracts COVID, I come Thursday, I was notified Saturday that my therapist has COVID, then my husband and I tested yesterday. We are waiting for results. Anyways, the care of my special needs SIL (SNSIL) has been transferred from me to my SIL as of a few months ago because I’m trying to find a job and move forward with my goals. Therefore, I have really stepped out and not handled any scheduling or whatever else. My SIL shows up this morning to take care of my SNSIL and she asks why we are wearing masks. I explained the situation and she FLIPPED. She cussed us out and came in our room (where we were isolated) and went off. Eventually we hear my MIL come home and she’s upset because we “freaked her out”. Now I’m pretty sure tomorrow, my SIL won’t come and we’ll be in charge of my SNSIL which I don’t want obviously because we need to be isolated. A few key notes:

1. I assumed my MIL caught SIL up. There was no reason for me to believe that me telling her the situation would cause an uproar.

2. My husband and I have only come out of the room to grab food and we wear masks and use sanitizer. We also stay away from everyone (6 ft plus). If we come back positive, we will not leave the room.

3. My SIL has gone home every day early due to drama. She also goes to estate sales, auctions, get togethers, Christmas shopping, etc. She is in no way careful.

4. MIL says we should’ve told her earlier but I’m like, that’s not our job? We aren’t arranging care for my SIL. We assumed she, as the mother, would make decisions and do what needs to be done.

5. Me, husband, MIL, and SNSIL live together.