I understand your dd's frustration with all of this.
I too have back pain, and mine is permanent. I also had a doctor who did nothing for quite awhile, and that's what led to mine becoming a permanent condition, at least, according to the specialists who I did see much later.
Obviously I don't know the exact details of your daughter's condition, but I too have herniated disks (three), as well as degenerative disk disease, and I still have this. These are only two of many problems that I do have with my back. Nothing can be done about this that the other problems won't undo any treatments done on this. So, I just have to live with this.
My doctor did do me one huge favour in the beginning, and for that I'll be forever grateful, although I wasn't at that time, and that was that he kept up on all of the newest treatments and research, and realized that bed rest was the worst thing one could do for a damaged back. He forced me to walk for half an hour three times a day. This was unbelievably painful. So much so that I often had to take someone with me, because I'd collapse in pain midway at times and need a strong shoulder to support me until I could bear to stand again. But I did what he said and gradually I was able to walk again. The pain remained for years, and I've always had to alternate activities -- standing, sitting, lying, walking, etc. -- but at least I could remain fairly active. I, like your daughter, cannot sit on a chair at a desk or a table for more than 20 minutes before I experience extreme pain, but I can do other things now besides remain in bed. I am typing now on a laptop on my couch with my legs extended. That's the only way that I can do this. I've found ways to work around this.
If I remain in bed for too long, my body 'seizes' up and I experience intense overall pain, the type that your daughter is likely experiencing, only a million times worse in her case. I can't begin to imagine what she is experiencing. I live in fear of being hospitalized with a fractured body, since this would require what your daughter is currently experiencing, and I don't think that I could ever bear that type of pain for days on end.
I honestly don't know how your daughter's problem will be resolved at this point. Any movement would put in her into extreme pain, but remaining there would intensify this pain. Only a specialist would be able to solve this puzzle, in a way that would work best for your daughter.
Unfortunately our health care system isn't the best at times, but at least it is there for us. That's how I try to look at this. It took me more than ten years to see some resolution to all of my health problems, but I'm gradually getting there. I'll never be completely healthy and whole, but I am finding that I'm gradually becoming more pain free and whole than before. I know that I'll always have to live with pain, but there is a big difference between horrific pain and just having pain, as your daughter well knows. And sometimes we just have to accept that.
All the best to your daughter. And I'm sorry that I haven't been able to offer anything of real value to you. :-(