Oy, I remember learning to ride a bike. I did it on a bike WAAAY too big for me (amazing I was able to have kids afterwards), and in an alley where I had to do low speed 180s to get any distance. Ugh.
Anyway, one silly thing. As a kid, I just didn't connect with the notion of balancing on a bicycle. It made no sense to me that the faster I went, the more stable it got.
So consider this. Sit her down on a chair and have her hold a bicycle wheel by the axle with both hands. Spin the wheel to get some momentum.
Now ask her to tip the wheel over. It will resist. That will get across the notion that the spinning wheel allows us to stay upright the way we do and the faster we go, the more stability we get.
For me at least, that little demonstration made me far more confident.
__________________
Proud parent of a happy inner child ...