The best advice I got from my vet when I was about an inch away from losing my mind with worrying about the Quality of Life my 15-year-old dog was having was to:
SPOIL HIM ROTTEN.
He had 3 different times when he quit eating altogether (one time as long as 4 days). I switched him over from dry dogfood to a good brand of canned food (the kind with all the chunks of meat and vegetables). On top of the stuffed-up nose and sneezing, his teeth had also been giving him problems that I was unaware of at the time. This change from dry to wet food started him eating again. After the 2nd time he stopped eating, I fed him small pieces of grilled hotdogs. This worked well for a few weeks. After he wouldn't eat hotdogs anymore, through trial-and-error I found the next incentive: shredded cheese
Like Missy, my dog would also have these unexpected surges of energy (running around in the back yard, etc) after having gone DAYS without eating and/or drinking any water. I still don't know how he had the strength and stamina to do some of the things he did.
What is a treat for Missy? Bacon? Hamburger? Whatever it happens to be, if making a meal of treats everyday will start her eating again, then that is what I would give her.