There's a reason to go see a sleazy, collegiate drugs-and-foul-play-and-ooooo!-lesbians B movie that features young celebrities-in-training rather than more established marquee names: The lower-profile performers have less to lose by getting down and dirty. In the case of New Best Friend, an exploitation thriller that's been sitting on the shelf since 2000, the key talent in question happens to be a trio of gifted actresses, but the principle still holds.
It's time for Mia Kirshner to get cast as something other than the decadent sugarplum she's been playing ever since Atom Egoyan's ''Exotica,'' but there's no denying that she's got the part down cold. As Alicia, a mousy good girl who goes bad under the tutelage of the campus bitch princess (Meredith Monroe, sharp in a dull role), Kirshner is naughty and soulful at the same time -- a combination that could take her far. Dominique Swain, so good in the 1997 ''Lolita,'' has a sexed-up vivacity as the lewd and troubled Sydney. The party scenes deliver some tawdry kicks. The rest of the film, in which Taye Diggs, looking lost, plays a cop investigating Alicia's overdose, is dudsville.