(1) Must be post-HP Book five, and post-BtVS S7.
(2)Ginny must find out she has amazing stength by doing something physically hurtful to either one of her brothers, Draco, or Harry (But she has to be very freaked afterwards).
(3)Buffy and Faith must come to Hogwarts and tell her she is one or the Choosen ones.
(4)Most people in the Wizarding world must know that a Slayer has a short life expectancy, causing them to be a bit upset when they find out Ginny is a Slayer.
(5) There should be Buff-ish (Like, the kind of phrases and add on's the Scoobie Gang uses...