Its her very first day home we got her late last night the pup is happy and playful but had a little bit of blood in her poo I have a vet appointment tonight but I need to know if I shojld leave immediately to take her as I own 2 cats and anothrr dog this girl is supposed to have all her shots but I'm worried

Common causes of blood in dog stool include parvo, parasites, over eating, new foods, hemoragic gastro-enteritis, and rectal injuries.

The question is does your dog have any other symptoms? Is she eating normally? Have you changed her food recently? Is she vomiting? Does she seem more sleepy than normal? Is she drinking?

If she's vomiting or lethargic get her to the vet ASAP!
Just in case I would call the vet anyway and see what they say. It can't hurt. Because she's a puppy and is playful I would guess that it could be worms or that her poop is too hard (new food, new place, and what not) but call just in case.

Let us know how it turns out!