She needs to finish the work and graduate. The school is in control and it has set out the requirements. It may seem like the school and teachers are being mean, but it is probably very disruptive to have a student constantly missing class and having to make up the work. It is a private school, and can set its own rules. Your daughter is entitled to a free and appropriate education, but not at this school.
Just have her finish. It’s a lot of work. It’s hard. It’s the only way to get to college.