Goo, do you know about the scooting method for learning to ride a bike? Might be what you little girl needs.
In case you don't: (and apologies if you do)
Take pedals off bike and put saddle low so she can reach the floor comfortably with both feet.
Encourage her to scoot along pushing with her feet. She'll start slow, but as she gets her balance, each step will get longer, and pretty soon she'll be freewheeling in between 'steps'. She'll be learning steering, balance and brakes, without the same risk of falling over and without having to cope with action of pedalling at the same time.
Once she's confident with freewheeling, steering and stopping when she wants to (if you can find a very gentle downhill slope, so much the better) you can replace the pedals and it'll be almost instinctive for her to pedal. Then you can start to raise the saddle gradually.
I taught a middle aged man to ride this way, in 45 minutes - showed him what to do and off he went and came back in less than an hour to have the pedals on, and away he went. Kids are pretty quick to learn.