why is my dog's poop black and watery and puking eveything she eats?
Black or tarry looking stool indicates digested blood in the stool. Digested blood in the stool indicates bleeding in the stomach or small intestines. This is potentially a life-threatening situation and should not be ignored. You can read more about this and the potential causes at the following site:
Since your dog is also vomiting, this could indicate severe pancreatitis, intestinal obstruction or even peritonitis.
As you can see these conditions can be life threatening, so I do urge you to have your dog seen as soon as possible. Since she is vomiting, it is unlikely any medication could be kept down, but pepcid or Zantac might help. Be sure an let your vet know if you give either of these.. Read about Pepcid dosages and usage information here: http://www.petplace.com/drug-library/famotidine-pepcid/page1.aspx
Zantac can be given to a dog at .25 to 1mg per pound every 8-12 hours. Read about usage here:
I hope this helps.