If you and me eat vegtables all week and nothing else then suddenley change to eating meat all week then our gastronintestinal system would be very upset.
The reason for the vomiting is the change in food or bad quality food. It wouldnt of helped the situation.
It is difficult to say why she has vomited in the first place but undigested food suggests intestinal problems , it may well be something as simple as a little bit of inflammation of the intestines that has caused this.
If the vomit is straight after eating (within 30 minutes then the problem may well be more serious (a intestinal blockage, such as she has eaten some bones that have become lodged) if this is the case she will require surgery to fix this problem - this is only indicated in vomit shortly after food.
I would feed her chicken , boiled fish, rice for 3-4 days then slowly introduce her normal food ( a good quality one) if the vomiting doesnt cease then i would advise a trip to the local vet
Please ensure her worming is up to date as this can sometimes cause vomiting
Hope this helps