Fireworks was my first thought too. One of mine is a real Nervous Nellie. She is a little quieter today than usual -- probably from being so stressed last night. I held her most of the time.
I was worried one of mine had a bad tummy today as someone had an accident in the house. Ben had not eaten well so I thought it was him. Kept all of the dogs right by me and .... another accident. This time I know it is Annie with the problem! So, I have one not eating & one with runs. Maybe New Year's Eve was hard on our pups?
For me it is actually a change of food that I believe is the problem. Have you changed anything? I saw where it was suggested to take her temp, also look at her gums (are they pink & moist?). Is she drinking plenty? I found when I first started running the heat, my pups were not drinking like they had in the summer. With a dryer house, they were getting just a little on the dehydrated side. Nothing big, but enough that now I keep offering water. They always take it when I offer, so they must need it. Hope it is nothing major and your little one is back to herself in no time!