OK, thanks for the additional information.
There are many different causes for vomiting. The most common cause is a gastritis/enteritis which is an upset intestinal tract usually resulting from a change in food or eating a new type of treat or table food. Sometimes, however, we can have gastritis even without a history of dietary indescretion.
The next possibility is that your dog has pancreatitis. It causes vomiting and sometimes diarrhea. Usually the front of the abdomen (just behind the ribs) is extremely painful in pancreatitis. The treatment for this disease is hospitalization with IV fluids and pain and anti-vomiting medicines.
The next possiblity is that your dog has swallowed an object that she shouldn't have causing an intestinal or stomach obstruction.
If your dog is not vaccinated, another possibility is parvo virus. This is more common in puppies, but can happen at any age. It usually causes great amounts of bloody diarrhea and vomiting.
It is also possible that your dog has a problem with her liver or kidneys as well which is a serious matter.
If your dog is still fairly bright and alert then you do not need to rush her in to the vet right away. You can try fasting her for 12-24 hours and then feeding a small amount of cooked chicken and rice. If she keeps this down then feed her this for a couple of days and then gradually mix in her regular food.
Some dogs with mild stomach upset will benefit from pepcid. If you would like to try this there is information on pros and cons and dosing found here:
If she is not bright then you can try giving her a small amount of pedialyte to get her through tonight and she should be seen in the morning. If you think she is extremely uncomfortable then an emergency visit is in order.
I hope this helps.