Hello again and thanks for waiting.
Sorry to hear Panda is unwell, however I have worked out an answer for you below ...
This may not be what you want to hear I know but what you should do just to be on the safe side is have a vet check her over sooner rather than later.
1. I say this because : While the symptoms you describe would not allow me or any other vet to pin this down to any one particular disease via the internet I would say from the fact that she is very lethargic and not eating that it is possible that your dog is running a temperature and so may be in the grip of some kind of infection. This would be the commonest cause of the symptoms you are seeing.
2. I normally like to suggest home remedies if I can do this safely but in your case I think it is not worth the risk as it could well be that prescription drugs such as antibiotics would be what is urgently needed if Panda is indeed running a temperature, but you should be aware that a range of other diagnosis are also possible.
3. In the meantime until you can get him to a vet all you can do is to keep her as comfortable and reassured as possible make sure she is taking fluids regularly, and try to keep tempting her to eat.
I am sorry I cannot safely give you any more specific advice via the internet.
I hope I have covered your question fully enough but if you would like further clarification or to talk things over a bit more then I will be on-line for the next hour or so and I will be more than pleased to continue working with you.
Please be kind enough to rate my service to you after we have concluded our dialogue, such feedback helps me maintain the quality of my answers.