Pretend Friends Forever. used when two people act like they're great friends, but then bitch and spread rumors about each other behind their backs. typically used on females.
Kate: Aww girl I love you so much!
Molly: We're gonna be friends forever!
Molly to someone else: oh my god kate is such a whore!
*Someone who overheard both conversations*: damn, Molly and Kate are complete PFFs!