My dog is very sick, parvo maybe?

I am taking her to the vet in the morning, but I'm very worried about her tonight, and wondering what this may be. She has had diarrhea, so thin it looks like brown water and throwing up white or yellow foam. She does eat grass often normally, along with lettuce and cauliflower (she loves it as treats) but she hasn't lately. We haven't changed her food, she eats Royal Canin German Shepherd food because she seems to love it and we raise shepherds so one feed is easiest. She has not been anywhere, no kennel or groomer or anything, and all of our other dogs are healthy, and up to date on all shots, heartworm and flea prevention, and worming, all that good stuff. She started this yesterday, but seemed better before I had a chance to take her to the vet so I figured she maybe at something bad, but tonight/this evening she started it again, and too late to take her to the vet. What could this be? Anyone have this happen? And was your dog okay? I've read the symptoms of parvo and it seems like MAYBE it could be that, but I certainly hope not.