I used to work with emotionally and behaviorally disturbed children and am a mother of 3 boys, one of which I suspect has Aspergers. Despite the diagnosis, the way to work with them is always the same-Structure and consistency. Develop a routine and help her prepare for it, especially if there is a certain time you know she'll go off. For example, so son used to have a huge fit when it was time to leave somewhere so when we were about to leave I would buckle him in the car annld go over the rules and how I expected him to behave and then what the consequence would be if he misbehaved. Then you need to stick to your guns. Setting limits will initially cause the behaviors to worsen if she is not accustomed to it, but she should come around.

The other thing is to try to discover what she is trying to gain through her tanturm. Make sure her behavior does not succeed in meeting her goal and process through this with her- Talk to her about what it is she wants. Ask if her behavior got her what she wanted. Then ask her what it did get her (her consequence). Help her find the words to express to you what she wants without a tantrum (she still won't always get what she wants much of the time, but teach her to express herself.

I would recommend bringing her to see a specialist. The school can be a good resource if finances are an option as they may pay for some things, such as occupational therapy or teaching you behavior management skills.

I would start sooner rather than later. As you pointed out she's already getting bigger. Not only is she harder to restrain, these behaviors are more strongly developed with age.

I hope thing get better for you.