My son was prescribed risperdal from a much younger age than your daughter. He has Aspergers (or whatever they call it now), but it was to help tone down his violence and aggression. He was incredibly violent and kept trying to kill his sister - literally murder her whenever he could. Risperdal is a heavy duty antipsychotic medication. It is also used in addition to mood stabilizers when they are not working to stabilize the moods of people with bipolar disorder. I have zero clue why it would be used for someone with autism but I would be asking a whole lot more questions. We asked a TON of questions before allowing our son to take it. If we hadn't been desperate, we wouldn't have tried it at all. It really scared me after I read about it. But having him sneak into her room at night with knives he stole from friends' houses scared me a whole lot more. It was a good medication for my son, and helped him a lot. He was on it for a number of years without many side effects. It let him stop and think through his actions more before he did things. He still did them quite often, but it was more of a choice than a compulsion,Know what I mean??
This is just my opinion, of course, but I think maybe your daughter needs some more traditional anti anxiety medications. I am not sure what you have tried - prozac worked well for me, but even the older medications might work - things like elavil or other tricyclics can be helpful and can be given in very small doses at night at first to see if they help. Start low and go slow!! I suggest the older medications because their side effects are VERY well known. Some make you sleepy the first week or two and then they don't. I have taken 4 different tricyclic antidepressants over the years for different reasons and they all worked that way. I have spoken to others who all said the same thing. The first couple of weeks after starting we were tired (and actually I am taking a tricycllic now for a sleep disturbance - it evens it out without knocking me out, just helps me get the REM sleep I need) but then that wore off. If our dose was increased, we were a little tired for a week maybe, but then we were back to normal. The trick is to take the first doses at night.
I strongly encourage you to seek out Occupational Therapy for your daughter. Read up sensory issues as they are a BIG problem with people with autism and greatly contribute to social anxiety. If your environment is incredibly uncomfortable - the lighting hurts and it feels like everything around you is attacking you, even the fabric of the chairs you have to sit on and the odor of the air you have to breathe, you are NOT going to be comfortable leaving your safe home where you are not attacked. There ARE ways to help. Many of those ways are through Occupational Therapy and DO NOT involve any medication.
I know that conventional wisdom is that the brushing therapy does not work once a child is 10 or 12 years old, but I think that is hogwash. Why? I learned about it when thank you was 7 and Jess was 10 and Wiz was 14. It helped each of them. I was a heck of a lot older than that and it helped ME. I have serious sensory issues and figured the brushing probably wouldn't harm me as long as we did it the right way. I was homeschooling Jess and she thought it was fun to do it to me, so I let her. I was shocked at the change! I reached in and yanked the cotton out of a medicine bottle one day and Jess' mouth fell open. I NEVER touch cotton balls in ANY form. I can't. They squeak and I just can't touch them. It didn't bother me at all, when it is something that has bothered me all my life. Our brains are more changeable, more 'plastic' as the docs call it, than we have any idea. I would work to get an Occupational Therapist (OT) to teach you how to do the brushing therapy and gentle joint compressions on your daughter, and then I would do them. Even if it is useless, at least it would be worth a try.
The book I recommend to learn about sensory issues and how to help them is The Out of Sync Child by Kranowitz. It explains it very well. Most libraries have it. Kranowitz also has another book that your daughter might be a little old for, but might not be, depends on her. It is called The Out of Sync Child Has Fun. This is a book full of fun activities that provide the kind of sensory activities, or sensory diet, that help a person with sensory integration disorder. Back when we had my youngest evaluated for autism etc..., several of the child psychiatrists and occupational therapists told me that sensory integration disorder is at the mildest end of the autistic spectrum disorder, and that almost everyone on the autistic spectrum has sensory problems to some degree, most of them to a greater degree than the general public (and their parents) understand. I don't know what fiction you like to read, but Christine Feehan wrote a paranormal romance with a heroine who is autistic. She did a great job of explaining the sensory issues but not making them book about the disability. Even if you don't like this type of fiction, it is worth reading to see the world through the woman's eyes. It is titled Water Bound and is a couple of years old, I think. I am sure it is available used by now.
I would actively seek interventions for autism for your daughter. Especially private Occupational Therapist (OT), and tell the therapist that you just want to try and see if the brushing therapy will help, among other things. After all, as long as you do it the correct way, it won't harm her. If you do it wrong, it can cause problems, which is why you have to learn it from an Occupational Therapist (OT), but then you do it at home. I also think addressing her anxiety with APPROPRIATE medications will help. I didn't respond to this earlier because I wanted to think about it. I don't have a medical degree, but for a nonviolent child without a mood disorder, risperdal seems a very odd choice to treat anxiety. I would want a more standard anxiety medication. I can see not wanting to go with the SSRI/SNRI medications given the black box warnings about suicide in teens/children, though they can be helpful. There are other medications like the ones I suggested. And ones I didn't suggest also, I am sure. The combination of these things will hopefully help your daughter.