Everything Timocela said.
And this -
If you decide an RTC is the only way to get your child appropriate therapy; and you want to keep her in her home state; you will have to file the beyond control - they have a "no fault" category for just such situations. You will have court dates and be assigned a case worker who will try and get you to do many varied useless things. This is one time you'll want to be able to document everything you have already tried. Stress the last resort aspect of your petition; and stress your desire to get your child appropriate long term therapy. You should have no problem proving it needs to be long term. In a case like this, giving the state custody is not by any means giving up your child. You will remain an important of her treatment planning and her life in general. (altho they may lie to you about this) IN a case like this, the state is not severing your parental rights, but rather, taking custody so as to provide a level of care not available to individual families.
The state worker may try and intimidate you into leaving them alone - but you must persist, if this is what she needs.
The benefits to your daughter could be manifest. I know MaryHurst and the Presbyterians have very good independent living programs, and scholarships to local colleges - and if she is and remains on the low functioning end of the scale (simply meaning she won't be able to hold a job, no matter how smart she is) they will help get her disability started (which may be more important for the health insurence than the money) but they do a good job of taking very low functioning girls and showing them that they can control their emotions and that they can enjoy success on the job.
Once again, let me say: Please don't take a short cut with one of these private owned programs b/c it seems easier. In the long run, it will most likely make matters much worse. Also, don't think that b/c they cost a small fortune they will provide better care - This is just not the case. And keep in mind, they have no one holding them accountable.
Do pay attention to Timocela's advice about her schooling. It is the key.