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I am sorry you dog is not feeling well.
The most important thing is that she is well and happy and alert as well as drinking.
It is normal for dogs to go through a period of unrest when in boarding kennels and often their appetite does reduce, and bizarrely I do see some dogs that will be 'in a mood' for a period once their owners have returned. So, in the short term you could test this theory and see if she will eat a healthy but different alternative to her normal food such as some scrambled eggs/cottage cheese/ mashed potatoes.
However, I would only do this if she otherwise seems well and is drinking and doesn't seem in pain, especially around the mouth.
If she is still not eating, or becomes unwell/off water then i would definitely get her checked by your vet. There will be some open today and tomorrow despite the bank holiday weekend. My first area to examine would be her mouth to make sure that there is nothing going o here that may be making it uncomfortable to eat.
Good luck and I am sure she will be fine