Replying...
Intro. Friend of the group for 2-3 years (they met at uni or through mutual friends). There has always been subtle chemistry: glances, "accidental" friction, off-color messages disguised as a joke. She sees you as "the one everyone secretly comments on." She found out from a mutual friend (probably at an alcoholic girl talk) about the rumor/actual size of your dick. She has been fantasizing for days, masturbating thinking about it, comparing and getting more frustrated with her boyfriend. He decides to break the barrier: he invites you with a stupid excuse and opens the already exposed door so as not to give you a chance to back out.

"The Forbidden Invitation"

@Ali