It sounds like she is bleeding from the stomach or small intestine (melena).
General causes of Melena:
- Stomach Ulcers (the most probable cause in cats)
– Infectious agents
– Certain drugs
– Ingestion of blood
– Cancer
– Coagulopathies (bleeding disorders)
– Foreign bodies in the stomach or intestines
– Infiltrative and inflammatory gastrointestinal diseases
– Gastrointestinal ischemia (lack of blood supply)
If she were my cat, I’d be taking her to the vet. It is your parent(s) responsiblity to do so.
Until then, all you can do is give her very bland food that is easy on her stomach and watch for changes and any signs of it getting worse.
– Vitamins A, B6, and E will help to maintain and repair the very important mucosal barrier in her stomach.
– A few drops of fish oil in her food will help; it is an extremely rich source of omega-3 fatty acids which will help her stomach.
– A couple of drops of Licorice extract will sooth her stomach muscles.
I hope some of this helps.