Yeah, Leia knowing Rey was … sighs… a Palpatine is honestly just dumb. It can be justified however way, but it’s lazy writing.

You would think that if Leia knew this, and that Palpatine was somehow still alive and Rey, his granddaughter, was going on a mission to stop him, that it would be better to find out from Leia, her master and someone she trusts, rather than Kylo or Palpatine, who would use that information to manipulate her.

Imagine Kylo being like,
Kylo: You… are a Palpatine.

Rey: I know.

Kylo: Wait, what?

Rey: Yeah. Leia sat me down and told me already. She really understood what I was going through, since her own father literally tortured her and destroyed her home planet. Despite that, your mother is one of the greatest people in the galaxy, and her heritage didn’t affect who she was and what she stood for at all. So, Palpatine being my grandfather has zero effect on me whatsoever. If her dad being Vader didn’t effect her, Palpatine being my grandfather doesn’t effect me. If anything, it solidifies my resolve to stop Palpatine, because that’s what Luke/Leia did already 30 years ago.

Kylo: Oh… well… I guess you know what you need to do then.

Rey: I do.