Hi Josh _ welcome
It seems to me that there are a few things going on here.
The 'romance':
Does she actually care for you and want to be with you?
The drugs:
Much more serious and definitely needing attention.
This will affect all aspects of her life.
You seemed to have been a good influence in this area, but someone else came along, enabling the weakness to take over again. She needs real help.
Drink driving:
Were you offering to drive her home while you were drunk?
This is what it sounds like.
This is very, very wrong and dangerous.
So important things first:
She needs help to get off the drugs.
You must never drink and drive.
Once you have both sorted out your lives you may find that you are right for each other ~ or you may not.
Things will sort themselves out.
Lovers' tiffs are commonplace ~ they can be overcome, as long as the important matters are sorted out.
Good luck