If everything else fails, you should consider getting more medical help.
Right now, I'm on an SSRI (zoloft). My psychiatrist thinks I'm predisposed to low levels of serontonin, because many a lot of people on my mother's side are on the same thing (mother, grandmother, aunts, cousins).
Also, you could try fine tuning her diet. I am currently reading a book called "The Ultramind Solution." It's specifically for disorders of the mind (anxiety, depression, etc), but has excellent advice for diet and everything else that matters for well being. Even though I started out with Heather's book, I only found success on a diet pretty different. If you've exhausted all your options and its not getting better, its time to make a change