Complex sentence: From 1951 until her death in 1961 she was a patient at Napa State Mental Hospital in Napa, California and died there at 91 years of age knowing only her name and that she was "an actress".
Split into simpler sentences: From 1951 until her death in 1961 she was a patient at Napa State Mental Hospital in Napa, California. She died there, aged 91, knowing only her name and that she was "an actress".