Welcome! You are not overreacting. You are like me years ago. My ex is like your girlfriend.
1) I questioned if she was an alcoholic
2) She only had 2 or 4 drinks. In actuality it was always at least double or triple what was stated.
3) She initially said she would get it under control. Would only drink at home. Then started driving drunk. Then started driving drunk with kids in car....
4) I was never controlling in any other relationship I had... Until my relationship with an active alcoholic.
Here we sit, 13 years later- 3 DUIs, 3 rehabs, multiple episodes of endangered kids, etc...
It will not get better for HER unless she decides to address her issue.
I have been going to Alanon for the last few months, which is full of people who understand and can relate what you are feeling. It is helping me to understand my contribution to the dysfunction in the relationship.