My suggestion is to take the dog to a board certified, veterinary ophthalmologist. Have your vet recommend one or find a vet in your area who can. This is a necessary test reputable breeders have done for health clearance in most purebred dogs before they are breed so you should be able to find one in your area.

A board certified, veterinary ophthalmologist will be more likely to tell you for sure what may be going on since your vet thinks it is "maybe" her tear ducts didn't heal over.