I'm no expert having only been a dog owner for 4 and a half weeks, but Nui had unexplained diarrhea for 2-3 of those weeks, so I sympathise. Has she been wormed? I know every vet is different but both ours told us to worm every 2 weeks initially. Nui's problems got better after worming, but it could also have been the pro-kolin we gave him. It's a prebiotic paste with fibre that binds them up, you can get it from the vet or chemist and he loved the taste. I also read that feeding earlier in the evening reduces the chances of them pooing overnight. Might be worth a try. Hope she feels better soon x