That’s not exactly how genetics works. My thinking is that they would simply duplicate Palpatine’s X chromosome to produce Rey, removing the Y in the process, or there would be a donor chromosome. Otherwise, she is exactly the same as him.
I do like your explanation for why Palpatine’s body is falling apart, though. But it’s also a good idea that he’s in that state because of his own selfish actions. He killed off all of the clones that were grown since “birth” because he was threatened by them, and is only using the one(s) that were “born” at the age where his genes were taken.