Not suggesting this as actual dialogue, but for the sake of conveying an idea I’ve been noodling that might tidy some of these ideas up with what we see onscreen:

“Long ago, Palpatine used the force to create life itself- to create the boy who would become Darth Vader. My grandfather was to be his heir. But the Skywalker line proved too strong in the light- he lost Vader, and he failed to tempt Luke. So he created life again- created you. Only this time, he poured in a part of himself. A part of his soul loves in you, Rey. A part of his power.”

I wouldn’t explain much more than that onscreen. It gives you Rey Palpatine with nobody parents, the Dyad if you like, plus how powerful she is early with little training.