So sorry to hear of your daughter's situation. My experience was very similar but I've made an excellent recovery. I, like you, posted a query on a board last year 'Does anyone feel they're getting worse on interferon?' I was stunned at the number of responses but the one that sticks in my mind was from a girl who replied:" Before interferon I was walking independantly, at 2 weeks I needed a cane and at 2 months I was in a wheelchair. I told everyone I thought it was the drug but friends family and doctors told me to 'keep going'."
This experience was so similar to mine. I started interferon as a 'precautionary measure' but was soon so badly affected I could no longer walk far or well and had literally innumerable symptoms. I was going downhill fast.
There are many people reacting badly to interferon. I'm not sure of the official number (about 3% my neuro told me) but I fear it is a lot higher than this. My problem with this is that I wasn't warned at all about this possible side-effect and with all the ensuing cognitive difficulties I was left to figure it out on my own. Not easy, I can tell you!
However, I would like to finish by saying that one year down the line I'm now doing great. Of course I stopped interferon immediately before it was too late, and started looking for other therapies. I found a little regimen that works great for me and has brought me back from the brink. No one would ever guess I had MS now. There is hope. Things will change for your daughter. You have to seek out and find the best possible treatments for her.
I wish you luck.