Reminds me of a movie, "Days of Wine and Roses" with Jack lemon.
They both drank, they got married, he got help, she didn't....,
He stayed with the help, recovered and he could not help her, she kept drinking.
He had a choice in the end, he could not help her after offering recovery same as he.
She left.
The enabling aspect of her mother is something you cannot wish away either.
When I drank, there was mom's "magic fridge", it was always full of food.
It wasn't until there was no more "magic fridge", "spare room", "fine and bill payer", ex and family courts when life became interestingly real!
I got hungry, slept under a tree, ( no bills by the way ) but had fines to pay off or face prison.
And even then it took me another 10 years, got a house, rent paid, bills paid, fridge full of food,the occasional traffic fine and STILL alcohol ruled me.
It wasn't until I realized, "where is everybody" after my last black-out drunk and life was meaningless even though I got up from the dust 10 years prior, the spirit was broken. Material things did not matter anymore....,
It may take your friend that type of journey in principle so she may one day look at herself.
These enablers did seem to prolonged my action to seek solutions and recovery in hindsight.
So it's not your fault, by moving on with your life, you are doing her a favor.
We can only hope and pray she ask's herself that inevitable question,
"where is everybody", and seek help herself.