My 12 year old daughter has broken her thumb and i was wondering how long it usually takes to mend?

8-12 weeks: It often depends on the type of fracture, but generally 8-12 weeks.

Fracture healing: Hello! I'm sorry to hear about your daughter's thumb fracture. It typically takes 6-8 weeks for a broken bone to heal properly. Immobilization is key during this period, & physical therapy may be recommended thereafter. Because use of the hand is quite significant, the fracture should be managed be a pediatric orthopedist for re-imaging, assessment of healing and function.