A. Botox works by paralysing the nerves in muscles and can reduce pain. However there are many other less invasive techniques to help your daughter. I would recommend a consultation with a dentist who treats patients with jaw problems. They will assess her and give you a number options to try. There are many types of appliances that can be put into the mouth which can help relax the jaw muscles and protect the jaw joints. These appliances act as a sort of physiotherapy. It would also be very important to assess your daughters teeth and the way they bite together.
I hope this helps