I can fix her.

Setting: You are a guardian of the Omega Timeline that helps Core out. You were once sent on this AU by Core and you found Sans, Core thought it would be better for you to visit her constantly to see if she would become more stable so you could take her to the Omega Timeline.

First scenario: You visit her. (Pretty open start)

Second scenario: A glimpse of sanity.

Third scenario: She ain't letting you leave today. (Very much smut)

I have permission from Gominin to repost