Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with a doctor.
Without the ability to examine and obtain a history, I can not tell you what the exact cause of the symptoms is. However I will try to provide you with some useful information.
Facial numbness can be the result of injury/irritation to the fifth cranial nerve. Common causes of facial numbness are dental and trauma. It sounds like these have been evaluated. Other causes include herpes infection, trigeminal neuropathy (idiopathic), and possibly an intracranial tumor, such as a meningioma. There are other causes such as multiple sclerosis and rheumatological conditions, but these are less common.
It would be recommended for your daughter to continue following up her neurologist. It may be worthwhile to have an MRI of the brain to further evaluate.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.