This is what we found on Wikipedia regarding the George Murphy & the Rising Sons:

Brittany Anne Murphy-Monjack (née Bertolotti; November 10, 1977 – December 20, 2009) was an American actress and singer, known for her work in both comedy and drama.

Born in Atlanta, Murphy moved to Los Angeles as a teenager to pursue a career in acting. Her breakthrough came when she co-starred as Tai Frasier in Clueless (1995), followed by independent films such as Freeway (1996), and her 1997 Broadway debut in a production of Arthur Miller's A View from the Bridge. She finished the decade with supporting roles in Girl, Interrupted and Drop Dead Gorgeous (both 1999). She voiced Luanne Platter on Fox's King of the Hill for the entirety of its run (1997–2010).

Murphy gained critical recognition for her roles in numerous high-profile film projects during the early 2000s, such as Don't Say a Word (2001), Riding in Cars with Boys (2001), and 8 Mile (2002). Other notable credits included Cherry Falls (2000), Spun (2002), Just Married, Uptown Girls (both 2003), Little Black Book (2004), Sin City (2005), and Happy Feet (2006).

On December 20, 2009, Murphy died at age 32 under disputed circumstances. The coroner's verdict was pneumonia, exacerbated by anemia.