You could take the crankset and chain off the bike and turn it into a large balance bike. Then once she's become comfortable using it as a push bike, add the crankset and chain back on and have her try pedaling.
Mostly likely you'll need to purchase a new bike in the near future. I'd think a tall 9 year old wouldn't properly fit most 20" bikes, and would be better served by a 24". For comparison, my normal height 5 year old can ride a 20".