Answer:
If someone vomit could they keep vomiting and not stop...And die from it
There are no cases reported of people dying directly from vomitting.
However, if you vomit often and keep vomitting for longer periods (a day for example) you should drink water in between to stop you from dehydrating.
Also, if you inhale the stuff that comes from your stomach it is very bad for your lungs and I assume you could die from that in several ways.
If you are vomiting for extensive periods of time please consult a doctor.
For more information search on Cyclic Vomiting Syndrome.