Whoa! I've just read the whole thread...
This girls behaviour is extreme. She is violent and persistent in her behaviour. I am very surprised that she is not on a limited recess timetable, where she is able to be fully supervised.
I have worked with a number of children who have required full time supervision in the yard, not allowed to go to the toilet alone and are on pretty tight behaviour contracts. These are students who have been suspended for less than what this girl is doing.
I think that you need to write a letter to both the school and the Department stating your concerns, include dates, times, places etc..
It sounds like the school needs assistance from the Department in how to deal with this situation.
Good luck with your meeting and as nice as you say they are, be assertive in your concerns and ask to be assured of your child's safety both in the classroom and the yard. If need be the department can attend meetings like this.