Some calming vibes headed your way!
Try and have a little faith in her though. If she's anything like you, i'm sure you've raised her to be a responsible/considerate young woman- so hopefully she learned well during her training course and will prove her responsibility.
Does she know what to do in case of a flat, the car stalling, hitting an icy patch of road, does she know how to change a tire...etc? I remember when i first started driving- what made me panic the most was driving in the snow/ice- because around here we don't get much, and i didn't remember what to do so it scared me a bit.
I would make sure she know's what to do in some common situations should she need help. Other than that, i'm sure she'll be just fine!!