This may be due to intestinal upset from a change in food, intestinal parasites such as worms, coccidia, giardia or a bacterial infection.Intestinal parasites are one likely thing to be bothering her. You can bring a fresh stool sample to the vet to be checked so the vet can give the right worm meds or antibiotics if the problem is a protozoan infection such as coccidia or giardia or campylobactor. This could also be due to a swallowed non food item that is sharp, large or irritating, ingestion of something toxic including plants, mushrooms, chemicals etc, it might even be due to an ulcer, or to a tick carried disease.
If you give her any fatty treats that could be causing pancreatic inflammation which you can read about here
Or a condition called Canine Hemorrhagic Gastroenteritis (HGE) which you can read about here http://www.sniksnak.com/doghealth/hge.html
Dogs can develop a food sensitivity leading to inflammatory bowel which you can read about here
For that a change in food to one with no ingredients the same as what you feed now might work for example a fish and potato based dog food or venison or rabbit etc.Seeing the vet to find out what is going on would be a good idea. For home care you can add some plain pedialyte to the water bowl to help with hydration. You can also see if bland food will help your pet feel better. I would suggest trying boiled chicken meat or hamburger with the fat drained off, mixed with really well cooked rice in a ratio of 1/3 meat to 2/3 rice to see if that works. It's not a balanced diet but OK to use for a few meals while working on controlling digestive upset. The fiber in the rice will help bind up fluids. I find using the pedialyte and the bland diet along with the meds from the vet often works to resolve infection issues and you can slowly get the dog back on a regular food diet as it feels better. I would not use any over the counter anti diarrhea medication as if this is from a bacterial infection you do not want the bowels to slow that much until the bacteria is treated. You can though see if the intestinal soothing meds such as Pepcid or Tagamet or Zantac will help. These are used for bleeding ulcers too so may reduce any bleeding from irritation.Be sure to tell the vet when you see them if you use any of these. You can read about dose amounts (and cautions) scrolling down on the pages here http://www.petplace.com/drug-library/cimetidine-hcl-tagamet/page1.aspx http://www.petplace.com/drug-library/famotidine-pepcid/page1.aspx http://www.petplace.com/drug-library/ranitidine-hcl-zantac/page1.aspx Hope this helps you!