Emily,
Several people here have been treated at
Duke CCC and have commented on their positive experiences. It is a Comprehensive Cancer Center. On the left side of their web page is a tab for "Make an Appointment".
Please do not let traveling distance be an obstacle. Get the BEST possible treatment for your mom. She has been through a lot already, and it seems that her oral cancer is an aggressive one. I recommend it be treated by knowledgeable doctors who have the most experience with oral cancers.
Duke would be my choice in NC.