On her new single ”Mississippi Girl,” Faith Hill insists that fame hasn’t given her a swelled head. It has, however, swelled her ability to sell plastic. Fireflies debuts at No. 1 on the Billboard album chart this week with sales of 329,000. (The one-new-studio-album-every-three-years strategy seems to be working pretty well for her.) Not sure I buy the singer’s I’m-still-a-country-gal spin (neither does EW reviewer Greg Kot, here). Check out the video from her Live 8 performance, still streaming at AOL Music, where she sounds a lot more credible rocking out to Janis Joplin’s ”Piece of My Heart” than on ”Mississippi Girl” two songs later. Which doesn’t mean I can get Hill’s current hit out of my brainpan.