Well, Albino, for the majority, I would certainly agree with the replies you've received. What you may perceive as "sulking" or "boredom" is likely just your low maintenance dog content with it's pack and lifestyle.

This isn't a guaranteed diagnosis though. You didn't mention any veterinary regimens or health concerns (with the exception of the limp), which could play a significant factor. Perhaps the dog doesn't like eating because of teeth issues, or bad digestion? The dental situation although doesn't appear entirely plausible, since you've obviously attempted to feed sustenance with a good variation of textures, ingredients, and even temperature

If you're unhappy, or concerned with your dogs average behavior, perhaps it's the home or environment that generates it. Have you exposed your pet to different habitats, or does she generally remain in a generic vicinity? Does she respond unusually, or atypical to foreign environments? How does she react to changes in her home; rearranged furniture, visits from new people and animals, lawn maintenance? Does she have trouble socializing with strangers or with your other dogs?

If things like this bother her, she may just have a confidence problem, which could be the answer to the 'going' issue.