Frustrating (baby mama drama)

My SO’s has a child with a woman who makes zero sense to me. I can only go off how I would act, so I feel she is so over the top. Tell me if you feel differently or see where she is coming from.

SO’s daughter came the weekend before last. When she came to our house she had a bit of a cough, but never complained to us about not feeling well. We took her back on a Sunday. On Thursday her mother text and asked, accusatory, what we fed her because she is refusing to eat and hasn’t pooped since returning home. Then later she calls cussing out my SO because she has strep throat and accusingly asking who at our house gave her strep. No one here has it. My kids are fine and when he said that she replies with “are you sure” ...

She then goes on a tyrant about how she hasn’t bothered to get her insurance yet so now she has a bill and somehow that is all his fault.

Their agreement means that SO doesn’t carry insurance because it isn’t offered through his employment, but supports her in other ways. How is this his fault? She was just attacking him and making him feel really bad and for what? Because their daughter started a new school and ended up with strep? (That Monday she started a brand new school). It’s just so frustrating. Not only did she take it upon herself to move 3 hours away, she she just goes above and beyond when things upset her.