It is so hard to tell an eager young dancer that she is not ready for pointework, but sometimes we must.
Some teachers face tremendous pressure to put students en pointe very young.
The bones of the foot are not fully-developed, strengthened and hardened until sometime in the teenage years. Naturally there is a great deal of individual variation. If a young dancer attempts pointework without proper strength and technique, there is a chance that she will permanently damage those not-fully developed bones. Body weight times momentum creates a great deal of force. If she has strength and technique, and if the introduction to pointework is gradual and under total supervision, everything should be fine.