My 4 year old dog cannot keep anything down. Including water. She has also had some diarrhea.There has been some grass in hervomit. Help?

I would go to the vet or animal hospital ASAP.
I know some people that had this same problem and the dog ate something she shouldn't have and if they wouldn't have taken the dog in when they did they said it could have been way worse.

I'm not saying that's what this is but if it has been happening for a while I would get it checked out by a pro.