Beauty pageant pretty Cara Serber, 33, played against type last season by faking a space between her perfect teeth, putting on a gee-haw accent and yukking it up as one of the trashy leads in WaterTower Theatre's Great American Trailer ParkMusical (a role she's currently reprising at the Addison playhouse through October 21). The tall blonde then vamped it up as the big-boobed Sharon Tate role in Uptown's adaptation of the pill-popping kitsch musical Valley of the Dolls. Singing Sondheim for Into the Woods or shaking her tail feathers as one of the down-home tarts in Best Little Whorehouse in Texas, Serber is hot stuff with both the music and the comedy. Offstage she's a North Dallas wife and mother of a Serber baby. Some of her neighbors, she says, never even knew she played the title role of a cheerleader-turned-porn-star in Kitchen Dog's production of the musical spoof Debbie Does Dallas. That's the life of an actress: Here today, whore tomorrow.