If she wants a car, she'll need money. If she doesn't get the money from you, she'll need to get a job and earn some money. If she needs to get a job, she'll need to be sober. It will be up to her whether she wants a car or alcohol more.
If you loan her the money, she doesn't need to make that decision.
That, to me, is the bottom line of our role in this. When we take away their need to make their own decisions, we enable.
Hugs - L