Thank you for your patience. From what you have described with fresh blood in the stool, it certainly sounds like Zizi does indeed have colitis. This can be due to range of things including anything from stress, to infection, to abrupt diet change, to intestinal parasites. Hopefully Zizi is up to date with her deworming treatments and be sure to do this today or tomorrow if she is due. A reliable product like Drontal or Milbemax generally do the trick.
Often the best plan for the treatment of colitis is sticking with a bland diet for a good 3 - 4 days before slowly transitioning back to a normal diet over several days. I'm not sure what diet Zizi has been on previously, but for the next few days, start her on something bland. You can either purchase a veterinary diet like Hill's i/d or Royal Canin sensitivity control, or you can make her a homecooked diet to feed for 2 - 3 days. For this cooked, boneless, skinless chicken breast and boiled white rice is fine. Hopefully she would eat this happily. You also need to make sure she doesn't get any other food, snacks, tidbits or treats during this time as this will cause the colitis to flare up again. After 2 - 3 days on a bland diet, you can slowly 'wean' her back on to her regular food. This needs to be done slowly over the course of a week given her symptoms.
There isn't anything else you need to do from home for your girl, and certainly don't be tempted to try human medication on her as these are mostly toxic to dogs. If things aren't improving after 2 - 3 days on a bland diet, you will need to take a fresh fecal sample to your vet for them to rule out an infectious issue here. I hope all of the above makes sense? If you have more questions or if I can help in any other way, please do not hesitate to ask! If you would like to accept my answer, please press RATE OUR CONVERSATION (I am not compensated in any other way). Bonuses are always welcome. Thanks! I hope to work with you again soon!
PS: If you have additional questions after you rate the question, you are welcome to request me for additional conversations if I am on-line or by beginning your question "Dr. E..." or "Pet-doc..." and others will leave the questions for me.