I'm currently going through this same thing. Did you ever get any answers? PLEASE email me at ***@****.
Definitely get her blood-work done. That should give some clues as to whether or not she is fighting an infection. If so, the solution might be quite simple such as a course of antibiotics?
Is she on any medication for "dog dry eye" or Keratoconjunctivitis sicca?
And did the vet say if this is immune-mediated or not?
It is definitely an inflammatory condition so there might be an auto-immune element which is more common.
There are a number of causes and it's important for the vet to find out which it is:
congenital (from birth), metabolic, infectious, drug induced, neurogenic (of neurological origin), radiation side effect, iatrogenic (side effect of medication or treatment), idiopathic (no known cause), and immune mediated.
Symptomatic relief may be similar in all cases, but it's important to find the root cause.
The inflammation may also be affecting her nasal tissues.
It must feel horribly uncomfortable if so, and she may have some difficulty breathing. (Like feeling you have a constant bad cold or hay fever and it may be painful) .
Maybe that's why she has slowed down and seems lethargic?
That is my guess actually, but take her back to the vet and see what is discovered.
This is quite a good article about dog dry eye: