It's not likely a coincidence that you grew up in an alcoholic home and now find yourself in a relationship with an alcoholic. Many of us subconsciously sought to repeat an unresolved relationship with an addict parent through a romantic relationship as an adult.
You are not condemned to having to repeat this cycle. You can walk away from it at any time and no one has to validate your reasoning. However I will add that it is worth exploring in therapy any unresolved issues from your childhood as the son of an addicted parent or you might find yourself repeating this same relationship over and over again.
I didn't deal with being an Adult Child of an Alcoholic until I had several disastrous relationships under my belt, and I hurt a lot of people along the way. I had to learn about how to have boundaries, and how to take good care of myself no matter what bad choices other people made. I had to learn that I was worth more than I could ever get from a relationship with an active addict.
And FYI, her drinking IS a perfectly good reason for not committing. It is a major problem and one that she doesn't seem interested in addressing herself. That does not mean YOU have to deal with it.