Hi,
I'm sorry to hear your daughter is in such a bad way. The thing that makes depression difficult to beat is that it convinces you that even if you did beat it, what would be the point? Would you really gain anything? It's a vicious cycle, but luckily it can be broken.
I would suggest two things which were beneficial for me:
1: CBT (cognitive behavioural therapy) - This is a type of therapy that looks at your core beliefs and trains you to behave and think in ways that make you less vulnerable to falling into another depressive cycle. It also trains you to think positively about yourself and the world, but not in a happy clappy false sort of way, in a REALISTIC way. It takes time but I found CBT highly effective and very helpful.
2: Diazepam (Valium if you are in the US) - Be VERY careful with this one. For one thing it's a highly addictive drug, for another, in some people it will alleviate depression very effectively, in others it will make it worse. Try a very small dose, 2mg maximum, and see if it helps, if it doesn't, don't worry, it will wear off within a few hours. If it does help though, like it helps me, you will find it works incredibly well. Don't rely on it though, save it for the VERY worst days and be sparing, consider it a get-out plan if she gets in a very bad state. Try a very small dose to start though, and never go above a 10mg dose in one day, preferably in a week. You will also need a prescription for Diazepam/Valium and doctors are loathed to prescribe it for depression (for good reason), but have a chat with them and ask if you can try it.
Other medications I found were effective are Citalopram, which helped with the depression, but didn't help the anxiety I had at the same time. I'm on Venlafaxine at the moment and that seems to keep me on an even keel 6 days out of 7. I always carry some Diazepam as a crutch, but after CBT and finding a medication that works for me, I rarely need it (maybe once a month tops).
I hope she finds a treatment that works for her soon! *()