The Pyramid of Amirah (Unabridged‪)‬

A young girl makes a bizarre sacrifice. Buried alive in a pyramid, she waits for a mystical experience. You will not guess the ending of this story, which was selected as one of the best fantasies of 2002.
Author James Patrick Kelly is a two-time winner of the Hugo Award and a 2007 Nebula Award winner. His stories appear frequently in Asimov's Science Fiction, and he writes the magazine's "On the Net" column. Publishers Weekly has called him "a meticulous craftsman in the demanding short-story form".