Thank you. There are quite a few considerations for such pain. Masticatory myositis - an autoimmune diesase affecting the muscles of mastication is best understood but we need to also consider the following:
maxillofacial trauma - no history of that
temperomandibular joint disease ("TMJ") - X-rays are necessary to confirm
bone and soft-tissue neoplasia - X-rays and/or CT are necessary
foreign body penetration (caudal to last maxillary molar, tonsillar region, pharyngeal wall, sublingual tissues - I would expect considerable swelling, fever, abscessation
ocular disease and space-occupying orbital/retrobulbar lesions - examination by a specialist veterinary ophthalmologist +/-X-rays, ultrasound suggested
other inflammatory muscle disorders - polymyositis, extraocular myositis, dermatomyositis, laryngeal myositis
It can be a challenge clarifying the etiology of Molly's pain. Please consider having a specialist veterinary internist (please see here: www.acvim.org) involved in Molly's case. Please continue our conversation if you wish.