My dog has diarrhea for about 12 hours. I given her rice and dry food and plenty of water which she drinks. What can I give her to stop the diarrhea?

You can give Imodium. Its 1cc per 1lb of body weight (examples: 2lb dog gets 0.20cc and a 5lb dog gets 0.50cc and a 50lb dog gets 5cc) So... keep her off feed for 24 hours than start feeding her SMALL meals of boiled chicken and rice or browned hamburger (grease removed) and rice throughout the day along with the Imodium. This should help reset the gut. You don't want to give Pepto Bismul due to the aspirin properties in it.

If the diarrhea doesn't resolve within a few days, you may need to see veterinary help.