Thanks for answering my questions. I really appreciate it.
It's hard to know for sure what is going on with Buttons. The first thing I thought was Horner's, especially since she has had that in the past, however, there are several other possibilities.
It's possible that this is laryngeal paralysis. We often see this in dogs with the symptom of really harsh, noisy breathing, but from time to time we do see dogs who have a problem moving their tongues as well. Although there's no definite treatment plans, often a dog will need to have surgery to repair this paralysis. You can read more about laryngeal paralysis here: http://www.veterinarypartner.com/Content.plx?A=2331
If you live in an area where there are a lot of ticks, then there's the possibility of something like tick paralysis. This is caused by a toxin that is released when the tick bites the dog. I'd give Buttons a real close inspection and see if there's a tick on her anywhere. If there is and it's removed, the dog will often recover in a short time. There's more information on tick paralysis here:
In a middle aged dog, we have to consider the possibility of some sort of nerve damage. The Hypoglossal nerve is the one that controls the tongue/mouth, and if that is injured or has something like a tumor near it, it can cause the dog to love function of the parts near that nerve. Treatment for things like this can range from surgery to medicine, but unfortunately, it often requires a trip to a veterinary neurologist to determine if that is the problem. You can read more about facial paralysis here: http://www.petmd.com/dog/conditions/neurological/c_multi_facial_nerve_paresis
I do think that seeing a specialist is the way to go, but understand if it's not possible to make such a long trip. If Buttons were mine, I'd actually see if there was another vet in your area that could see her. It's very common for vets who practice in the same city (and sometimes even in the same clinic) to have very, very, very different educational backgrounds and experience, so it's possible that even though your vet may not know what to try, another vet in the area might.
I hope this helps.