(TMZ) - Lisa Robin Kelly - who played Eric Forman's older sister on "That '70s Show" -  has died, TMZ has learned. 

The 43-year-old actress passed away in her sleep Wednesday night at a rehab facility in California. 

TMZ spoke with Kelly's agent who say the actress had just voluntarily checked herself in for treatment this past week ... and was determined to clean herself up. 

The agent tells TMZ, "She had been fighting demons for a while and finally lost her battle."

Kelly had been in a downward spiral for the past couple of years - she was arrested at least 4 times in the past 3 years for DUI, spousal abuse and assault. 

Lisa had filed for divorce from her husband Robert Gilliam back in July - seeking to end a marriage that was littered with allegations of spousal abuse, by both parties. 

Besides "That '70s Show," Kelly had appeared in several movies and TV shows.

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