The transformation is complete. Kate Nash, the cutesy British pop singer who scored a major hit there in 2007 with the catchy little pop ditty 'Foundations,' took a decidedly punk rock turn on her 2010 album, 'My Best Friend Is You.' Two years later, she's fully embraced her inner punker with 'Under-Estimate the Girl,' a raucous rocker that sounds a bit like Courtney Love doing her best Karen O impression -- if Karen O had a faux British accent.

Kate Nash carries that punk aesthetic over to the no-frills video for 'Under-Estimate the Girl.' Sporting a new look -- her cute burgundy bangs and colorful pastel dresses replaced by long brown hair with dirty blonde streaks, striped shirt and, of all things, a bindi -- Nash managed to write the song, record it and even shoot the entire video in less than 24 hours.

Nash recently relocated to Los Angeles to begin working on her follow-up to 'My Best Friend Is You,' due later this year. But 'Under-Estimate' isn't the disc's official first single -- it's more of a place holder until that album is complete. Nash writes of the song: "So the other night I was stressin' out and we'd just finished rehearsing and I was like ARGHGHHGHGH I need to write a song and release something and do something creative instead of breaking all my stuff that I own."

Breaking all the stuff that she owns? We told you she's gone punk rock!

Watch Kate Nash's 'Under-Estimate the Girl' Video