Your g/f must get under a doctor's care right away if she isn't already. This woman has many issues to address and you cannot do it on your own. Her medication is not working. She is also using Vicodin which is very addictive and at the rate she is popping the pills, it sounds like she is addicted. The withdrawal from this is pretty intense, I have heard. Is she properly diagnosed? Is she clinically depressed or bipolar? Is she the one that told you about her diagnosis or a doctor? What about her family? How have they been coping with this in the past?

I think that the thing that you need to do is inform yourself. If your g/f is seeing a therapist, then maybe start by talking to the therapist. Tell him/her about the situation and get some advice. If she is not seeing a therapist, then get in touch with a local mental health centre and get some resources.

The worse thing you can do is get into her emotional headspace and be depressed yourself. Remember, she is suffering from a mental disorder which skews perception and thinking. Be supportive and loving but get some support for yourself. Find time to go out with friends and family to decompress. But get some information and advice from a professional source who knows how to deal with this type of situation. Good luck!