I'm with Freya. I'd reduce the hours and if things don't improve I'd pull her out.
Are there any other schools around besides the Steiner school who may be more sympathetic and understanding if not experienced in educating special needs kids?
I'm incredibly sad for her (and frustrated for you) that her teacher really doesn't get her autism. Are there any aides available that could advocate for your daughter? (ie does the government fund any additional support for both her and the teacher?)
It just sounds horrible that she's being told off for behaviour that's out of her control It's very upsetting.