Welcome!
What a difficult situation. I can not even imagine the A in my life being my grandmother. I was very close too mine too. She passed away many years ago and i still miss her.
The "only" (it was enough) i had with drinking was with my RAH. I can only suggest to try and see if al-anon is a fit for you, and start reading, reading, reading. It helped me a lot. I hope you can find a way that is healthy for you so you can have a good start into your totally new life.