I completely agree with your child. Senior year is too busy and short to mess with dealing with a flake. Check her universities and I would contact the Registrar at her desired universities to find out the requirements for her college diploma.
My 3 children had this experience with their AP Spanish teacher flake.
( I’m bilingual Spanish and English is my second language.)
My kids are bilingual, but are native speakers with “diminished” grammatical skills, so they took Spanish for native speakers. The Spanish teacher was not a native speaker, taught AP, but for some reason, she believed she became a native speaker by osmosis or something. She was cruel to her students, played favorites, and outwardly admitted this to administration, but she had tenure.
Once my kids got their 4th year in, they were done (MS Spanish classes helped). They avoided her like the plague. She wanted my kids in her AP classes. I was on staff and had my kids transferred out of her classes and she would intimidate the scheduling clerk to transfer them back. I had administrative approval to transfer my kids out because of their sports schedules. (AP Spanish was always held at the end of the day and our kids had HS games and tournaments. She hated the kids in sports. This teacher kept trying to get my kids back to the point that she would corner me in the halls and try to intimidate me! I told her she needed help.)
My kids were often humiliated by her, in class, because she made them her “favorites” and caused the other students to ostracize them.
Life is too short. Keep her out of the weirdness and let her do her senior year requirements in peace. She’ll be too stressed next year with all of her applications, essays and waiting.