You cannot reset or load their memory of it away, yes.

[ Agrees Chara breezily when the Sunkern laments his tweenage angst. That is when they'll accept the wrapped treat from him, though, opening up the wax paper with a delicacy that quickly changes to something more hurried (perhaps even excited) when they realize what he's brought with him.

So it goes, them nibbling at the treat as whatever it was that had upset Flowey is described.

Chara has never met Lusamine. There's a noticeable parallel here, though, just from what Flowey tells them. They finish their current bite of chocolate before speaking. ]

... I see. Suffering from an empty nest, do you think?

I wonder who it was she lost. [ A pause, as they settle themselves atop seating of their own. ] I wonder if she's dreaming of them now.