While we're at it, here's a photo of the bike in question.
I built it about a month ago. I've been commuting to work with it while breaking the engine in and getting the bike adjusted properly. (not to mention avoiding my pedal bike during that awful heat wave.) I haven't quite turned it over to her yet but it looks like I can do it within the next day or two. Right now I'm doing some final adjustments on the drive sprocket and chain. I think it'll be ready then.
Back when the OP was fourteen years old I let her use a happy time equipped mountain bike for her paper route in a nearby, rather hilly, area. She did well. I recall her repairing the clutch lever mechanism on her own when it popped out of joint. I seem to recall her doing other small repairs in the field and I don't recall needing to go out and help often. If ever, for that matter. So she's already one of us.
Now she's a young lady who needs to get to school and to work. I can't afford to let her burn up our car (the way 18 yr olds tend to do), so it's a motorized bike for her. Of course, we'll give her a ride when the weather's really dismal.
Anyway, you're liable to hear from her again for advice. Though I'm willing to be the mechanic when necessary, I won't always be available exactly when needed. And it'll be good for her to understand her machine in any case.