How did frankie valli's daughter die

Frankie Valli (born Francis Stephen Castelluccio on May 3, 1934 in Newark, New Jersey) actually lost two daughters. First his stepdaughter, Celia, was killed in a car accident in 1980. A mere six months later a drug overdose claimed the life of his daughter Francine. The loss of Francine is portrayed in the movie Jersey Boys when Valli gets a phone call while on the road. The first time he saw that scene Valli said "it was incredibly difficult [...] That lives with you forever."