You're My Person, and this is where it comes from

Burke: What is your problem?
Cristina: You know everyone’s back. Everyone’s back except her. And I listen to her. Everyday, about her McLove life, her McDreamy, her McCrap. And the one day, the one day I have a thing she disappears.
Burke: Meredith, this is about Meredith.
Cristina: She doesn’t know yet.
Burke: Meredith?
Cristina: She’s my person.
Burke: Right. And if Meredith doesn’t approve, then what?
Cristina: No, no. This, This is not about getting her approval, its about…
Burke: What?
Cristina: Telling her makes it, makes it... If I murdered someone she’s the person I’d call to help me drag the corpse across the living room floor.
Burke: Okay, now, you’re likening someone here to a corpse. I’m done.
Cristina: She’s my person.