I would try feeding her plain rice before giving medicine. Even minute rice is fine. Make sure she is drinking enough. I'd get her checked out if your vet is open tomorrow just to make sure it's not something serious. If there is they have meds that clear it up and if it's nothing they can give you the right dosage for a pup so small. I've given Loki pepto in the past but he had already been to the vet and they gave me the correct dosage.
Make sure you can identify any new food or treats that may have caused it. With the exception of the one time Loki had giardia, every time he got diarrhea as a pup (and it was like 10 times) I had given him something new. Finally when I got him on a better food (Canidae) he stopped having issues, plus I learned what he could tolerate and his tummy got a little stronger as he got older. | 