What have they done to our Kelly, those canny men pulling the strings of her post-American Idol career? Her single last fall, “A Moment Like This,” signaled that she might be headed toward the Mariah-Whitney-Celine radio-ballad sausage mill. Thankful puts those fears to rest: The album’s producers jam Clarkson into the stilettos of MTV sexpots ranging from Faith Hill (“Low”) to Vanessa Carlton (“Just Missed the Train”) to Christina Aguilera (“Miss Independent”). Her high notes are sweet and pillowy, her growl is bone-shaking and sexy, and her midrange is amazingly confident for a pop posy whose career is tied for eternity to the whims of her American Idol overlords. Thankful is testament to marketable young ladies with more talent than artistic freedom.