I am sorry that you are having this problem with your dog. The vomiting is likely a consequence of the excess water intake and whatever is causing her to drink more. You see, when a dog drinks more water than usual it is a sign an underlying medical problem. There are many possible causes. It will be difficult for me to pinpoint the exact underlying cause without a hands-on examination and some testing, I am sorry. But, common causes are an active infection, hormonal disorders (diabetes, cushing's), kidney or liver disease and even cancer to name a few causes. To determine which of the above is the underlying cause your family veterinarian will need to do some blood work (chemistry profile, T4 & CBC) and urinalysis as an initial screening test. Treatment will be determined by exam and test results; highly recommend having her checked as soon as you can for the above test. In the meantime, this si what you can do for the vomiting:
1- Do not give things like Pepto Bismol or Imodium. Start her on Pepcid AC (famotidine) 10mg 1/2 tablet every 12 hours. You can buy Pepcid AC over the counter in any pharmacy.
2- No food or water for 3-4 hours. Need to give her gastrointestinal tract time to rest.
3- After 3-4 hours offer a small amount of water. Wait half hour, if no vomiting, she can continue to have water but don't let her drink excessively. Leave her without food for 6-8 hours then offer a small amount of rice (50%) and boiled boneless chicken or ground beef (50%) 4-6 times a day.
4- Follow up with your family veterinarian for a hands on examination. If cost is a concerned I would look into your local ASPCA or Shelter where they often offer veterinary services at a lower cost.
My goal is to provide you with excellent service - I hope I've provided the information you were seeking, if you feel you have received anything less, please reply back as I am happy to address follow-up questions. Kindly rate me when you are done.