While 12-year-old Gaby Hoffmann, TV's newest child star, gazes calmly into a camera at L.A.'s superstudio SmashBox, her mother, Viva, 55, the high-cheekboned vamp featured in Andy Warhol's underground films of the 1960s, paces nervously a few feet away. ''Watch the nymphet thing,'' she warns as the photographer coaxes Gaby to bare a shoulder. As Gaby pulls down her sleeve, Viva winces. ''I'm just an anxiety-ridden harridan,'' she says. ''Gaby's just the opposite. She's completely happy no matter where she is or what she's doing.'' Gaby suddenly stops posing and looks irritated. ''That's not true!'' she yells. ''What about the time your sister tried to kill me?'' Viva pauses thoughtfully. ''I forgot about that,'' she says. ''Well, apart from my dysfunctional family, Gaby's usually pretty happy.''
Though moments of high drama are apparently routine in their lives (the two later claim Gaby exaggerated the fight with her aunt and was not hurt), Viva's observation seems right: Gaby, best known for her role as Jonah's pal Jessica in last year's Sleepless in Seattle, comes across as a grounded and serene, if precocious, preteen. But the star of NBC's new comedy Someone Like Me will never be mistaken for the kind of Valley-bred, assembly-line sitcom kid found on shows like Full House or Step by Step. Nor is her mom, who breast-fed Gaby until she was 4 and now manages her career, the typical stage mother. ''She's strange,'' says Gaby. ''Every day is different with her. Sometimes I feel like the luckiest person to have her, and sometimes she embarrasses me.''
Though they seem closer than most mothers and daughters, Gaby and Viva (née Susan Hoffmann) are an odd couple. When they aren't squabbling like the Bickersons, they crack each other up with one-liners delivered with the deadpan timing of Jack Benny. ''Mmmm, your chin smells good,'' murmurs Gaby as she burrows her face next to her mother's for a photograph. ''But your breath doesn't.'' ''God!'' howls Viva. ''What does my breath smell like?'' ''Dead fish,'' says Gaby.
According to Gaby, it's that kind of, uh, candor that will be a hallmark of her engagingly written series, which has just begun a six-episode tryout on Monday nights, temporarily booting Blossom to Saturdays. ''They built this show around me,'' Gaby explains. ''It's about an 11-year-old girl and her family and friends. She's like a smart-ass, very opinionated. She lies to her mom and stuff. But it's realistic. They don't say something bad and then make up and everything's resolved in two minutes. It's like real life.''
Of course, real life for Gaby has been anything but a Hollywood sitcom. She and Viva claim Gaby was conceived a week after her half sister, Alexandra Auder, now 23, told her mother she wanted a sibling and the two prayed for a baby at the Our Lady of Fatima shrine in Portugal. Gaby won't, however, talk about her dad, a soap opera actor whom she has not seen in three years. She began acting in commercials at 4 to help pay the family bills but got tired of the work and quit. Then, Viva says, ''her competitive spirit got the better of her when she heard that Macaulay Culkin was getting $5 million a movie.'' At 6, she got back into the business and made her first film, 1989's Field of Dreams.
Until last summer, Gaby had lived her entire life with her mother and Alexandra (before she went off to college) at New York's notorious Chelsea Hotel. The Chelsea is where Dylan Thomas lived in an alcoholic haze in the '40s; where a drugged-out Edie Sedgwick set her room afire in the mid-'60s; where Sid Vicious fatally stabbed girlfriend Nancy Spungen in 1978. Viva and Gaby left in July after a longtime dispute with the management (Viva says they ''liberated'' the vacant apartment next to theirs by breaking down a door with hammers), but the hotel ended up figuring prominently in Gaby's future. Someone Like Me, in fact, was hatched after one of the show's producers, Gail Berman, read a New York Times article about the Chelsea that mentioned an as- yet-unpublished children's book that Viva and friend Jane Lancellotti wrote titled Gaby at the Chelsea (a takeoff on the classic Eloise).
Now that she and her mother are ensconced with their two Eskimo dogs in a two-bedroom rental house in Woodland Hills which was badly damaged in the January earthquake, Gaby says she misses her former home, where she and her best friend, Talya Shomron, would roller-skate in the hallways, spy on the drug dealer across the hall, and dispatch the bellman to fetch ice cream at night from the neighborhood deli. ''I miss my friends, the subways, even the people I hated,'' says Gaby. ''Here I have to rely on my mom to drive me everywhere.''
Viva is even less enthusiastic. ''I hated every minute (at the Chelsea),'' she says of her 32 years there. ''Now I miss it terribly. L.A. is a living hell. I went from total anarchy and chaos to manicured lawns and cypress trees. I've had two migraines from the repression of these manicured lawns.''
Misgivings about their new digs aside, both mother and daughter are committed to the show, Gaby's first series after well-received supporting roles in The Man Without a Face (1993), This Is My Life (1992), Uncle Buck (1989), Field of Dreams, and Sleepless. Gaby says she loved working with Nora Ephron, who directed My Life and Sleepless, as well as with costars Tom Hanks, Mel Gibson, and the late John Candy, but she found Kevin Costner ''bossy.''
David Letterman really managed to get on her bad side after she appeared on his show in 1992. ''He's so rude and mean,'' she says. ''You know how Sean Young is supposed to be a bitch? He asked me if I was related to her. I'm sure he's acting nicer now that he's on earlier and makes more money.''
Viva and Gaby have not fared too much better with men off screen. ''I hate men,'' says Viva, who has not had a relationship in three years. ''I'm so glad I'm through with that. Whenever I'm sexually attracted to a man, that means he's bad news.'' Gaby had a boyfriend in New York, but the two have broken up. ''It's a long story,'' she says ominously.
Though Viva admits to worrying occasionally whether show business ''is the right thing for Gaby,'' her daughter is unfazed. ''I wouldn't be doing this if I didn't want to,'' she says. Her mother knows that's true. ''Gaby's always been like a little adult from the day she was born,'' says Viva. ''Things don't get to her.'' Gaby looks annoyed again. ''Oh, right, Mom,'' she says witheringly. ''What about the time you and Alexandra tried to kill each other at my 10th-birthday party?''
Viva rolls her eyes and sighs. ''Okay,'' she says, ''so we're not perfect.''