You got it. Put it in writing, how her drinking affects you, and then distance yourself the best you can. Give her time to let it sink in.
I ruined thanksgiving for my children, ages 13, 19 and 21 and the older two still are not talking to me. I am devastated to say the least. Alienating my children was the "rock bottom" I needed to hit.
Just know that she may drink even more as a response, if she has no other resources to cope with the pain it will cause her. Maybe have a phone number to AA for her in case she doesn't have it. She can call the number and they will put her in touch with a recovered female AA member to help her and they are usually on call 24/7. You can also call the number first yourself and talk to them, let them know your plan to give your mom the number. They'll be a good resource for you. Thats how AA works, by working with those still suffering, helping them get sober.
Good luck and know that you are not alone!