They're hot (if not Maxim material); they harmonize (take that, TLC); they play guitar, bass, cello, and tambourine; and they've been doing it for around 15 years. Still, you've probably never heard of Betty, so get acquainted with this trio of fab femmes at midtown Manhattan's Zipper Theatre. As you guzzle wine in cushy car seats, Alyson Palmer, Amy Ziff, and Elizabeth Ziff embark on a riotous, rockin' autobiographical journey chronicling Betty's basement beginnings, bathroom breaks, even therapy sessions. Lots of therapy sessions. Plus, they provide their own soundtrack, flush with addictive pop-rock-alterna tunes like ''The It Girl'' and ''Jungle Jane.'' Peppy recorded interludes by the Go-Gos and the Spice Girls inject a note of irony into the evening: Mainstream success may have eluded Betty, but the band plays on. Forget Destiny's Child. These are the real survivors.