Keep in mind as you read this, that I have no real experience working within a company structure like you probably have. I kinda do right now, but I've never even met the HR person, and I go to the office about three times a year... So I really don't know what I'm talking about (except the first paragraph below).
First of all - when confronted with a safety issue, like driving a vehicle you're unfamiliar with in adverse conditions, you made the absolute right call! I have to do this all the time - turn down flights in a helicopter, that another pilot would make (and I accept flights that another pilot would turn down, it's all comfort zone with specific conditions and missions). I would imagine your hotel might have a training program you're supposed to go through before you operate company equipment in an official capacity, and if they don't, they should. If driving that thing is going to be part of your duties, get out in some good weather and drive that thing around (on company time - it's got to be on their insurance, and you need to be paid!). Get out on the highway, and through downtown a bit at least, see how it handles.
I've never dealt with a coworker that nasty before, but IMHO, you should not stand for it. Since you've already considered quitting, think of it this way... If you quit, you won't really be able to use this job as a reference, so try to take her down with you (or preferably, get rid of her and keep your job). HR should get rid of her in a second if they find out that their job is getting harder because of her (they have to hire more replacements for the people she makes quit = more work for them). In addition to documenting each instance of harassment as flippedgazelle recommends, it might help to get statements from the personnel who quit recounting their experiences with her. In all likelihood, HR and other supervisors are at least somewhat aware of her manipulations, but they find it easier to ignore her than replace her for now.
The biggest thing is don't let her get to you, remember that no matter what it feels like, you can literally walk out the door at any moment and not look back - just remembering that can help you ignore her... just do a good job, and remember, your focus is on school right now anyway.
Now if you're scared she might go on a shooting rampage, well then all the above rambling is for naught - run!