As the bespectacled preteen prude warning other kids that Del Monte's Vegetable Classics are dangerously easy to make, 10-year-old Michelle Collins of Chino, Calif., is TV's newest, cutest huckster. ''Kids, we're in trouble,'' she says as sidekick Michael Nunes, 4, holds up the box. ''They could show up at any meal.'' The 12 spots, which began airing in February, play off children's suspicion of all things leafy and have given fourth-grader Collins who's partial to broccoli celebrity status. ''I was in the grocery store and a man shouted at me, 'Hey! That's the girl on that commercial!''' she says. ''I ran right to my mom.'' Collins, whose father is a plumber and whose mother manages her career, has appeared on Full House and Family Ties and recently completed the TV movie The Haunted for Fox. Now, like a seasoned star, Michelle plans to lie low for a while and spend the summer poolside taking swimming lessons.