Having completed a 21-city mall tour in April, during which she tested out material from this, her second CD, Avril Lavigne knows who her fans are: teenage girls who love to shop and watch a lot of TRL. But since the release of Lavigne's 6 million-selling debut, 2002's Let Go, other girl rockers like Fefe Dobson, Katy Rose and Lillix have joined the anti-Britney brigade. Heck, even Hilary Duff is cranking up the guitars. Under My Skin, though, shows that Lavigne, now 19, still rules the mall-chicks-with-attitude crowd. Easily avoiding the sophomore slump, Lavigne hasn't let go of her rebellious spirit on crunchy, radio-ready pop-rockers like "He Wasn't," which, with its racing rhythms and tough-talking lyrics, recalls the punk spikiness of "Sk8er Boi." She continues to kick boyfriend butt on songs like the piano-driven "Together" ("When I'm alone I feel so much better/And when I'm around you I don't feel together") and the feisty first single "Don't Tell Me," which gives a sense of empowerment for resisting pressure to have sex. Developing her artistic independence, Lavigne's solid success here is all the more admirable because it is achieved without the hitmaking production team the Matrix, which was largely responsible for crafting her influential sound on Let Go. Instead, Lavigne cowrote six tracks with fellow Canadian singer Chantal Kreviazuk, while also collaborating with former Evanescence guitarist Ben Moody. On the brink of her 20s, Lavigne seems to realize that the teen-angst angle will soon get old. She actually sounds surprisingly upbeat on the buoyant "Who Knows," while moving beyond boy-conscious concerns on the emotional ballad "Slipped Away," about the death of her grandfather. For now, however, Lavigne smartly understands that it's best to keep things from getting too complicated for her fans.