HI-
Red orange diarrhea with mucus shows that the lower bowel, colon, is irritated and producing mucus to alleviate the irritation. Many things can irritate the colon, one of which is viral entities, worms, lack of fiber in the diet, and many others.
If you're not seeing worms, then you don't know if she has worms as the eggs are microscopic, and she has been dewormed already. It takes about 3 weeks for eggs to show up in the stool after deworming. Your vet should check her stool for eggs today with vaccinations.
Your puppy is described as eating and playing. Parvo virus is very debilitating with vomiting/diarrhea and not eating, laying around a lot without energy. That is not how you described the dog.
I would see your vet today as planned for a thorough physical exam.
I hope this is helpful and will ease your mind until your appointment.
Thanks!
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Dog Veterinarian
27+ yrs of Veterinary experience: medicine, surgery, nutrition; 40+ yrs.companion animal owner