Girlfriend's mom is an alcoholic, and its killing my gf, how can I help?

All you can do is do what your doing, be there for your girl. get and understanding of the whole disease of alcoholism. Can be hereditary but also being humans have freewill and also learn from there environment, doesn't mean every off spring of an Alcoholic is domed to it. AA's Big Book have chapters for the family. My opinion AA Alon literature is the best and would give you a good understanding. It's been working since 1935.