There are normally two phases to treat children with crowded teeth.
The first phase is what we call the 'interceptive' phase where children are seen as young as 8-9 years old to determine if an expander is needed to expand the jaws and encourage teeth to erupt in a better position. Hopefully this may prevent any teeth extraction due to crowding later on. Some children may not need this phase and hence they can move directly into the second phase.
The second phase which is the 'definitive' phase is where fixed braces are used to correct malalignment of teeth and this can be done when the patient is in late mixed dentition ie: only a few baby teeth left. Normally for girls, this is about 10.5-11 years old.
Saying that, it is better to see an orthodontist at a younger age as you wouldn't want your daughter to 'miss the boat' as such.
Hope this helps. Good luck!
