Echoing what Guldy said, set the seat low so she can comfortably touch the ground and have her just stride around on the bike first to get a feel of how to balance, steer, and use the brakes. Maybe even take off the whole crank/chain assembly and make an adult version of the Strider®. After she has balancing down, throw in pedaling. What trips up many beginners is trying to pedal, balance, and steer all at the same time. Master them one at a time and it will be a piece of cake.