by Bruce Fretts & Lynette Rice

BUFFY'S SISTER ACT
Sarah Michelle Gellar's ''Buffy the Vampire Slayer'' is about to get a little sister -- or is she? Creator Joss Whedon confirms that The WB's occult hit will add a regular character, a 14 year old girl named Dawn who has darkly psychic powers. So is she Buffy's blood relative? ''It's more complicated than that,'' teases Whedon. ''But they become like squabbling siblings.'' (Dawn will also develop a crush on Nicholas Brendon's Xander.)

Whedon says ''Buffy'''s not suffering from Raven-Symone Syndrome -- the tendency of aging series to add adorable tykes, as NBC's ''The Cosby Show'' did in 1989, in an attempt to boost ratings. ''The WB certainly didn't say, 'Can you add a moppet? Everyone likes a moppet!''' Whedon maintains. ''Dawn is not there to be cute and cuddly.'' Yeah, that's what they said about cousin Oliver.