Hello till: I'm sorry you find yourself in such a difficult situation. Unfortunately I don't know if there is much of anything you can do here beyond what you've already thought of. Speaking with your mother's, & your, doctor is a good idea I think. He can't talk to you about your mother. But I don't know of any reason why he can't listen to what you have to say. It also makes sense to call the police if your mother is endangering herself, your sister, & others on the road with her driving. Of course, where you live makes a big difference here too. Laws vary from one place to another.

The only other thing I can think of would be, if there is a child protection agency where you live, probably a governmental agency... possibly county or state, you could try calling them particularly given the driving situation. But again, depending on where you live, that might not result in much of anything or it could end up being the "atomic weapon" of actions, so to speak. It's not something to be taken lightly. I'm afraid that's the only other thing I can think of. Your mother is an adult. And she has the right to make her own decisions... including bad ones. If she simply won't deal with whatever's going on with her, whether it is some form of addiction or perhaps some undiagnosed medical condition, there's probably not much you can do to force her, I don't believe. My best wishes to you though...