This may be due to intestinal upset from a change in food, intestinal parasites such as worms, coccidia, or giardia, or she could have a bacterial infection such as campylobacter, listeria, or salmonella.
This could also be due to a swallowed non food item, ingestion of something toxic including plants, mushrooms, chemicals etc.
So seeing the vet to find out what is going on should be a priority.
An over the counter med you might try would be Pepcid or Tagamet or Zantac.
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
If that helps then you can see if some bland food and plain pedialyte added to her water bowl will help her.
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.
But if she is vomiting and having diarrhea a lot, then if you can see your vet with her today you should try to do so.
Dogs that are vomiting can end up dehydrated pretty quickly.
You can check for dehydration by pulling the skin gently up over her shoulders in a 'tent' and release it. If it goes right back down that is good but if some stays stuck up that's a dehydration indicator.
If your dog might have gotten into anything toxic, is getting dehydrated, has a rectal temp over 103.5F (normal is 100.5-102.5F), has gums or tongue that look white, blue, gray or yellow tinted where they are normally pink, has a slow color refill if you press on a pink area of gum or tongue, or is becoming lethargic and non responsive to you then I'd get the dog in to see an emergency vet if one is available in your area.
This site may help you locate an emergency vet if you need one
http://www.vetlocator.com/hotline.php
Hope this helps you!
Dog Expert:Rescue, Train,Breed,Care
30+ yrs dog home vet care & nursing, rescue, behavior&training, responsible show breeding, genetics