Here's the latest update:
The vet looked at daisy's poop under a microscope and didn't find anything odd. She said the next strategy is to put her on a high fiber diet. She sent us home with a proscription dog food called "wd." So far, the food seems to be working. Her poop is improving.
In short, the vet didn't seem too worried about the whole situation. I guess we're taking it step by step. It's probably a case of a little too much worrying (let's hope so at least).
Thanks for all of your support guys, you rock!