I am just asking this for curiosity. Normally females have two X chromosomes, but in every cell, only one is active and the other is curled up into something called a “Barr body”. So a woman is a mosaic, with adjacent cells perhaps having made the opposite choice of which X to inactivate.
There must, however, be more to it than that. For you wouldn’t expect any abnormality to result if a woman had only one X chromosome, only she wouldn’t be a mosaic. Every normal male has only one X and no abnormality results. But that is wrong. A single X female is definitely not normal, see Turner syndrome - Wikipedia for details. Can anyone explain how this differs from what happens in normal females?