You get in a bus that she (or us if it could be made as the quest to get out peacefully) made from one of those "drop in water and watch it grow" foam toys, but for a vehicle. You get in it with her driving and launch out of the mouth-door without feeding it any juice. That may be a nice opening for it that could also be fun.
Also with the bus dropping you off, she could realize that she like driving better than teaching the worst students ever, and act like a fast-ish travel to places?
For your first suggestion, I personally like it. Different route, different experience, similar result.
For your second paragraph, I think that's a little too idealistic. Mrs. Slitherss, soft side or not, is prone to injure, even take the lives of her students- just for getting wrong answers, no less- who is fanatically loyal to an unseen monarch, and deliberately lies.
Unless we get a new update that makes Mrs. Slitherss non-violent altogether, her becoming a friendly transport service seems an eerie change of pace. Better she stay a foe to fight; goodness knows after driving you out to the outer world she'd be angry to have you back having skipped on the field trip.
