Honestly, my serious advice. You did ask.
Tell her that she needs to go to a treatment facility for addictions and depression issues, not live in your house. Agree to drive her there, and nowhere else.
You have a gf that has suicidal issues. She is drinking in your home, on top of 3 different anti-depressants, which could easily cause her to overdose, possibly even death.
You are enabling her why? Because you are getting what you want out of the relationship.
The best way to help her would be to not help her at all, because it's not help, it's enabling, and a trade-off, for what you want out of the relationship. In regards to her life, and her life alone, you are helping yes--to postpone her getting well.
I'm sorry if that stings.
Help is what professionals can give her. Help is what she will seek if she found rock bottom. She's a ticking time-bomb.