The more relevant question is how long she would have lived if she had not done this.
I was thinking that the estimates I've seen were that thirst kills you in around a week depending on your ambient conditions and physical exertion; being in a hospital and doing little would seem to extend the expected duration before thirst kills you. Unless Kim were some sort of super-girl who could set world records for surviving weeks without any water, that strongly suggests that the food/water deprivation was what actually killed her.
http://www.alcor.org/blog/?p=2716
Previously on LW: Aug 18, Aug 25, Aug 27, Jan 22.