If this is new and she hadn't acted out for a long time, I would check for things triggering it. In the past she may have been able to deal with the feelings that come with not getting what you want, but with added stress, she may not be able to cope. Anything going on at school, with parents, friends, etc.
Also, clean up her diet. Diet affects our behavior and can make any of us fly off the handle more, become angry or even depressed. Cut back on sugars, chemicals, and "non-foods" (processed foods). Also, environmental toxins. Get rid of any toxic household or personal products. They can definitely affect our brain and behavior among other things. You can check out my site and contact me for information on this. I'll be glad to help out. We've had to detoxify our home due to our son who is on the spectrum as well. Side note: This has been crutial to his recovery, and he is recovering.
Also, check out the book "New Kid By Friday" by Leman (I think). Also, as Dr. James MacDonald of Communicating Partners says, "Don't talk to bad behavior."
By the way, I have a son on the spectrum as well and my real challenge is my daughter too. LOL
Hope this is a help to you.
Blessings,
T. E.
www.LiveWellShopSmart.com
www.LovinLifeWithHomeBiz.com