Family sources told TMZ Reynolds died at a Los Angeles hospital of a stroke, hours after 911 was called to the home of her son, Todd Fisher.
"She wanted to be with Carrie," Fisher told Variety.
Reynolds, 84, complained of breathing problems, an unidentified source told the Los Angeles Times.
Margaret Stewart, a spokeswoman for the Los Angeles City Fire Department, said paramedics provided medical aid in the 1700 block of Coldwater Canyon Drive, and a woman in fair to serious condition was taken to Cedars Sinai Medical Center. The woman's identity, age or symptoms were not revealed, citing privacy laws.
TMZ reported Reynolds was at her son's house discussing funeral plans for Carrie Fisher, 60, who died after a heart episode last week on a flight from London to Los Angeles.
Reynolds earned her only best actress Oscar nomination for The Unsinkable Molly Brown in 1964. She earlier starred in "Singin' in the Rain" in 1952. She acted regularly into the 1990s.
She sang the No. 1 hit tune Tammy in 1957.
On TV, Reynolds starred in The Debbie Reynolds Show in 1969, but the situation comedy lasted only one season.
She earned the Lifetime Achievement Award from the Screen Actors Guild in 2015.
Reynolds was divorced from singing sensation Eddie Fisher in 1959.
Reynolds was married two other times -- divorcing from millionaire businessman Harry Karl in 1973 and real estate developer Richard Hamlett in 1996.