What’s not to like about Amanda?

This is a terrific time to be in the Amanda Bynes business. The actress, who just turned 17 last month, has a Top 10 box-office movie in theaters (“What a Girl Wants”), a starring role in a fun TV series (the WB’s “What I Like About You”) and ambitious plans to make the transition into more mature roles in the coming years.

Like fellow teen-queen Hilary Duff, who also has parlayed cable-TV stardom (the Disney Channel’s “Lizzie McGuire”) into a concurrent film career (“Agent Cody Banks,” “The Lizzie McGuire Movie”), Bynes has been working toward all this for some time. She started in commercials a decade ago, moved quickly to a role on Nickelodeon’s “All That” and then landed her own show, “Amanda,” a short time later. Her first theatrical release, “Big Fat Liar,” also hit it big with the 7-to-17 set.

Her pleasant, girl-next-door looks and gift for lightweight comedy and physical stunts on Nick eventually drew the attention of Tollin-Robbins Productions, the outfit behind the WB’s top-rated show, “Smallville.” The producers thought she’d be perfect to play kid sister to “Beverly Hills, 90210” alum Jennie Garth, who plays 28-year-old Valerie on “What I Like About You” (tonight at 8 on the WB). Bynes is Holly, 16, who is allowed to move into Val’s New York City apartment when Dad gets transferred to Japan.

The siblings bond, clash and generally get into Holly-inspired trouble. Tonight’s amusing episode, in which a festering feud with a neighbor threatens to get Holly bounced from the apartment for good, is no exception. Bynes handles the quick-tempo comic bantering like the seasoned pro she already is, and Garth holds her own as the brittle, uptight half of the equation.

A double-threat star at the tender age of 17. Isn’t that what every girl wants?