I think that, besides having fun - which is of utmost importance with kids otherwise they give up and choose to do something that is more fun and less distressful -, after they learn to keep balance and speed up, I'd say the next things must learn are to brake properly and to control their trajectory.
That said, one of the most exciting things to do, in my humble opinion, is to play tag (chasing game), or "follow the leader", in a park, taking turns on who is the leader.
When you are the leader (of course, not going too fast), she has to chase you and so she learns to do quick turns, brake, and change directions on demand (reactive).
When she is the leader, she develops her ability to read her surroundings and form trajectory-planning strategies in her mind (proactive).
Motor control resides in the cerebellum, and it must be automated by exhausitve repetition until it becomes automatic. There's no better way do do it than by playing and having fun, specially if it involves bicycle riding skills. It literally "grows in you". (I think that's why people say that no one ever forgets how to ride a bike).
Hope this helps