Build her confidence first, the rest should follow.
Lower the seat so she can touch ground comfortably while seated (standard bike fit/adjustment is not applicable until she's ready). Pull bars back a bit if you can, giver her upright position, not attack/forward mtn biking.
Go someplace paved and FLAT, large old abandoned parking lot maybe.
Go someplace without other people around, so she won't worry about them watching or colliding.
Slowwwww and easy, get her confidence up, and only try new things when She is sure She is ready.
Good luck!