Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry that you have been waiting for a response, but your requested expert isn't online which delayed your question coming up on the list for all to answer. I would like to help if you are still interested in an opinion.
I am very sorry to hear about Bella having bloody, watery stools and vomiting yesterday.
Of course anyone would be concerned about blood in the stool. The fresher it appears the closer the source is to her rectum.
The important factor in all of this is how Bella is feeling otherwise. If she feels great otherwise and is active, bright and alert then those are good signs.
There is a condition in dogs called hemorrhagic gastroenteritis. These dogs have profuse dark, jelly-clot like, bloody diarrhea. They are very sick dogs and get dehydrated quickly so they need immediate care. Thus if she seemed lethargic and/or continues vomiting that would be a likely possibility and care at an emergency veterinary clinic is best.
But bloody diarrhea is usually due to colitis, or inflammation of the large intestine, which can be due to stress, a change in diet, parasites, a bacterial (salmonella) or viral (Parvo virus or Corona virus) infection, inflammatory bowel disease or even a mass in the colon. Exposure to anticoagulant rodenticides is another possibility.
Do you know of anything that she may have gotten into?
I understand that you are concerned, but she is in the best possible place getting the supportive care she needs. In most cases as long as this isn't related to a large quantity of an anticoagulant toxicity they do well with supportive care of fluids and antibiotics.
Please let me know if you have any further questions.