I'm not a parent myself, but most of the parents I know have similar feelings. I'm sure you have made mistakes, but that's part of raising a kid. If your daughter has depression, though, that's a health issue that should be addressed by a doctor, and it's not your fault. Have you taken her to a doctor or a therapist? That might be helpful.
Also, I noticed that it's been about a month since you posted this... has your situation at home improved at all?