Something like the following as a WIP:

“You’re lying.”

“I’d never lie to you… your parents were no one… junk traders expecting a child they were incapable of producing.”

“Don’t!”

“Much like Vader’s own mother. An unknown slave with a miraculous conception."

“I don’t want this!”

“Palpatine chose you."

“No!”

“Your parents fled across the galaxy as he hunted you.”

(Rey sees the vision of her parents and her abandonment.)

“Why did the Emperor come for me?”

“Because clones are flawed hosts. He influenced the Force to create two dark bloodlines. My grandfather’s. Then, perfected with you. You… are Palpatine’s heir.”

“You were created to inherit the legacy of the Sith as a Palpatine. But what he doesn’t know is that we’ve become a dyad in the Force, Rey… two, linked by raw power. We can end him and the Sith, and create something new, together…”

Obviously the dyad is what I’d prefer but it isn’t strictly necessary as you’ve pointed out. It would just need mouth modifications and AI lines of Palpatine at the end there which might not work very well.