Once when I was in high school my parents went on a short vacation and left me at home (those were diferent times I guess.) Anyway, my mother's dog wouldn't eat and her nose was either hot or cold (it has been a LONG while ago), she was lethargic. I took her to the vet and it was just a "missing mom" thing but I felt so much better once I knew for sure! I still remember how worried I was.

I vote for "take her to the vet!"