EXCLUSIVE
Elizabeth Pena -- who became famous playing Ritchie Valen's brother's baby mama in "La Bamba" -- died from complications from alcohol abuse.
According to the death certificate -- obtained by TMZ -- Pena suffered from cirrhosis of the liver "due to alcohol." She had the disease for months, but it became acute shortly before her death.
The death certificate says the 55-year-old had acute gastrointestinal bleeding hours before her death, which caused her heart to stop.
Pena died October 14th at Cedars-Sinai Medical Center in L.A.