Parvo is not as common in adult dogs as it is in puppies. Is your dog's parvo vaccination up-to-date? Parvo is a core vaccine so if your dog is current on her vaccinations, most likely you have her covered (albeit some rare exceptions to the rule). If your dog has never been vaccinated for parvo before or she is not current, then that may be a different story.
Many more common issues can cause the symptoms you are seeing. For instance, dietary indiscretion, inflammatory bowel disease, a bacterial infection, giardia, coccidiosis, etc. I would suggest you see your vet for proper diagnosis and treatment and don't forget to bring a stool sample to your vet.