I don't see any validation for the guilt you carry.

It appears you were not in a position to make any such decision, or, as you just shared, you would have. Obviously, she wasn't able either? Were you in charge of her, were you given authority to watch over her and keep her safe? Then, and only then, would you have been negligent to provide that safety...but became selfish by drinking and not being in control. She had her own responsibility to be in control of her actions, and if she also took herself to a point where that didn't happen, you aren't the one responsible, even if she blames you.

I'm sorry you are still suffering, and it sounds as though she is too.
We all make mistakes.
It's important that you learn from any mistake you feel you made. (The mistake not stopping her, but in drinking so much you couldn't make what you now think were wiser choices.)

Solidify your learning points from the situation. That might help you move on from it.