Quote from Monica in The One Where Ross Hugs Rachel
Chandler: When are we going to tell Rachel what actually is going to happen? Monica: Soon. I just couldn't before. I mean, you saw how upset Joey got. I couldn't do that to her. She's my best friend. Chandler: Well, Joey's my best friend. Monica: I'm not your best friend? Chandler: You just said--! Of course, you're my best friend.