Oh how awful for you. And bless her too, what must she be going through?
Is she willing to talk to a substance misuse service, or perhaps you could? If you ring FRANK ( google it) they can tell you where the nearest one to you is. sounds like she hit a real low last night.
You are doing all the right things, you are good mum.
Try and keep your strength as hard as it is. In one shape or another you are managing day to day.
Much love.