I have SLE and Psoriatic Arthritis, when I was diagnosed some years ago I was prescribed Pred. The side-effects were the reason I was weaned off it and now I am a "Pred. refuser" (this was done with the help/advice of my Rheumatologist/GP/Neuro - fortunately they all communicate!). One of the worst side-effects for me was the mental side of things, so I can understand what you are going through with your daughter. Continue seeking their advice and maybe keep a symptom diary (sounds weird but it is useful to have with you when speaking to the Drs.).
All the best and hope your daughter feels better soon.