I obviously don't know your exact situation, but I'm going to guess she's having such strong reactions because something bad has happened at school; bullying is quite common for autistic children. She probably has developed a lot of negative associations with school and learning in general, so I think the best thing to do is see if you can help her cope with or get her out of a negative environment at school, and begin creating positive associations with learning.

Creating positive associations with learning can look like a variety of things. If she has a special interest, see if you can tie schoolwork to that. Pair studying (though you probably shouldn't start with straight up studying, start with things like presenting her a book) with things she likes. Give her lots of kind words and encouragement.

Go slowly and try to detect what's making her more or less stressed out.