Oh goodness, having a tiny one can be so scary
I almost lost my Luna, and she wasn't even that tiny, really. I talked with a breeder in my state (found her at YTCA.org) and she gave me a formula to make that saved Luna's life! This was after a crappy vet gave me care instructions, that if I had continued to follow, would have killed her or at the very least made her diabetic. Nutrical is great for some times, but shouldn't be over-used, as it seems to cause a quick spike in blood sugar, then the plummet
Anyway, lemme see if I can find a link to our story, where the formula is
http://www.yorkietalk.com/forums/showthread.php?t=58036
Force feeding isn't easy, but if it saves their life, that's what you have to do. Fortunately, I was able to get Luna to eat on her own very quickly, and I hope that you have the same result
Prayers going up that your little wee one is okay
If there's no improvement I'd get her to the vet ASAP. If your vet isn't overly concerned, then it's time for a new vet, since a lot of them have little to no experience dealing with toy breeds and tinies.