[MikeandRaph87]

Erin Moran grew up on the small screen as Joan Cunningham, Richie's(Ron Howard) younger sister and Chachi (Scott Biao)'s love interest. She fell on hard times due to drugs and hard partying. Eventually she ended up in an trailer park in Indiana with her husband. No cause of death was given, but it is believed to have been caused by a drug overdose when she was found uneesposive in her trailer.
https://www.yahoo.com/tv/happy-days-...012117080.html

https://www.yahoo.com/news/erin-mora...215726567.html
Despite wide belief, including my own, she died not of drug overdose, but of throat cancer. Those in her inner circle were well aware but did not mention it publically.