I'm looking for a fic that took place in season 1. Finn's just found out that Puck is the baby's father, and storms out of the room. For whatever reason, Rachel has followed after him. He turns around quickly and ends up smacking her accidentally because she was closer than he thought she was.
I don't remember the exchange, but she goes back to the choir room, and the glee members what are there are pretty shocked and angry with Finn. But Rachel is like, "why do you care?" (I'm pretty certain she even asks that.) And then, if I can recall correctly, the club shuns Finn (but he's still part of the club).
I think it might be Faberry, because I read a lot of Faberry, but I honestly can't recall enough of the fic to remember if there is a pairing.