Hiya
I think your doing the right thing in taking her to the vets but try not to worry about the blood in the poo. Poppy had this for ages - but the blood was bright red - i took her to the vets and she had a sensitive stomach and the food i was feeding her was agreeing with her.
The vet told me that if the blood is bright red then it is normally nothing to worry about, its only when the blood is brown/black that it could be something serious.
Good Luck, hope shes ok.

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Kelsie