Hi Shyrose, it's hard to accept, but you won't be able to stop your mother drinking, not by keeping a tally, or having a serious talk, or crying, or any other way.
Although that's probably not what you want to hear it does take a lot of responsibility off your shoulders. For now the fact is you have a mother, and she happens to drink. She may stop by herself, but it will be because she's worked through it and come to her own conclusions. I speak from experience as my parents drunk a lot at one stage and it caused a lot of unhappiness, but it didn't stop them.
You can set up some boundaries for yourself about about what you will allow while you're around. An example would be you won't listen to drunken phone calls. I think it's best she stays at a hotel because otherwise you'll be finding bottles hidden around your house.
My condolences on your losses. What an amazing long lived family you much have to have great grandparents only recently passing.