Are there any equine vets or specialists out there?

It sounds like nerve damage, or a neurological condition affecting the muscles of one side of her mouth. Since she isn't choking her feed, it sounds like only the lip and part of the tongue may be involved. The vet will have to do neurologic testing to determine that. In the meantime I would watch her when she eats, just in case there is any disturbance in her ability to swallow. I'd get the vet out asap.