Dealing with Teacher mood swings

You ever know a teacher either you had or your child who changed moods with their class?

My daughter has a class where first term she had something like a 99 average. My daughter loved the class, it was engaging and all her projects she was getting A plusses on.

Recently the teacher started going the opposite. Freaking out at the class being more angry, etc. There was one assignment she had told the class she would extend to Monday from Friday evening. On Monday almost the entire class was told they would get a zero because they did not complete it it by Friday evening, seemed she forgot she had extended it.

My daughter got a concussion on Friday so when I saw the zero I asked her about. I followed up with the teacher and the teacher said she would not allow my daughter to complete it even though we have a doctors note explaining her workload needs to be adjusted.

How to deal with this unreasonable teacher.