Is she pooping on a regular basis? (not pooping could signal a blockage)
If she is eating and pooping okay she may just have a sensitive stomach and she gets upset when her tummy is empty. We have had that problem with Shelby but it has gotten better as she has gotten older. She doesn't eat quite as much carpet
crud anymore.
Be sure to talk to your vet about it at your next visit or call if the problem continues.