Mild: Braces and elastics (rubber bands)
Moderate: Lower teeth extractions + braces
Severe: Braces + jaw surgery
Note: sometimes we can use a "reveres pull face mask (headgear)", but at age 13, this may not be as effective as if used at young age.
An Orthodontic Specialist is definitely recommended to advise in these cases.
There are several possibilities for treatment of underbite. It's best to get a free consultation at a certified orthodontic specialist to find the correct course of action. Hope that helps.
No one size fits all in orthodontics!!
The recommendation will probably be that she should have orthodontic treatment now while she is still growing, and possibly more at age 16 when she stops growing.
Unfortunately, this question does not have a simple answer. There are a lot of different possibilities for your daughter's treatment. The only way to know for sure is for you to make an appointment with an orthodontist and have a thorough clinical examination and diagnostic records. This will give the orthodontist all of the information that they need to thoroughly study your daughter's individual case and determine the best treatment for her.
I hope this helps.