1997. I don' know exactly when, nor do I know exactly how, however through my research I have found she died from a drug overdose.
Sid Wyman died in 1978.
Sid Womack died in 1958.
Sid French died in 1979.
Sid Chaplin died on 1986-01-11.
Sid Youngelman died on 1991-12-15.
Gary Oldman, who plays Sid in "Sid and Nancy" was given Sid's real necklace by Sid's mom. He wears it in the film too.
Sid Brews died in 1972.
Sid Crowl died in 1971.
Sid Boyling died in 2006.
Sid Tanenbaum died in 1986.
Sid O'Flaherty died in 1967.
Sid Helliwell died in 1939.
Sid Corfield died in 1941.
Sid Catlett died in 1951.
Sid Sackson died in 2002.
Sid Grossman died in 1955.
Sid Scales died in 2003.