I do not know if anybody ever watched the show on late night Nickelodeon called, "Are You Afraid of the Dark?" but it was a horrible show. I only remember one episode and that is because I had horrendous nightmares about the show for days. This one episode also happens to be the only episode I ever saw (my parents thought shows that give kids nightmares are not good shows to watch), and it is titled, "Doll House."
To make a long story short, a girl gets trapped in a doll house and starts to fall apart. She looses her fingers and toes first, but soon legs fall off and then arms. In the end she escapes, but only before she loses her ears. She comes out of the house looking like a soldier hit by a grenade. Beloved reminds me of this story.
Chapter 14 (titled "Doll House" in my book) is a short chapter that describes Beloved's fear of falling apart. Beloved takes a tooth out and fears that her "head on her neck, her legs attached to her hips (158)" will be next. This chapter is no doubt bizarre, but why does Beloved start to fall apart?
It must be Paul D and Sethe. "The couple upstairs, united, didn't hear a sound (159)." Beloved needs Sethe to keep herself together, which also explains why she is here. She is here for Sethe, and Sethe alone. What exactly for, I do not know, but this chapter amplifies Beloved's dependence on Sethe.