Kelly was 43, according to her biography on the Internet Movie Database."Lisa had voluntarily checked herself into a treatment facility early this week where she was battling the addiction problems that have plagued her these past few years. I spoke to her on Monday and she was hopeful and confident, looking forward to putting this part of her life behind her. (Wednesday) night she lost the battle. Cause of death has not been issued yet and no death certificate has been issued either," Wyckoff said.Kelly played Laurie Forman, older sister of Eric Forman, played by actor Topher Grace, on "That '70s Show," which ran from 1998 to 2006.