You dog may have acquired kennel cough. It is described as a "dry, harsh cough with a terminal retch" - meaning there is a gag at the end. Often times this gag brings up some clear fluid with it. It is usually exacerbated by activity, so the coughing is worse when she is playing or breathing hard. Infectious bronchitis (kennel cough) is a very contagious disease and is commonly spread between dogs in day care situations. It has a 1-2 week latency period (the time between exposure and the beginning of symptoms) so it may have come from a dog she was in contact with 1-2 weeks ago. Kennel cough is usually self limiting and not usually life threatening, so sometimes in adult, otherwise healthy dogs, I will not give any treatment and let it 'run it's course', shich is usually does in 1-2 weeks. However, if your dog is very young, very old, or otherwise immunocompromised (on chemo drugs or immunosuppressive durgs) or if the symptoms worsen I would recommend treatment with antibiotics from your vet to prevent pneumonia or other potentially serious consequences. I would also recommend you not take your dog to day care, as she may infect other dogs there.
Having said this, if you feel that this is more of a 'true' vomit (abdominal effort with retching, usually producing food or stomach contents / bile) and/or she stops eating, becomes lethargic or has diarrhea, you should get her checked out by a vet to make sure it's nothing serious.
Hope this helps! Good luck!