Her business manager and close friend Bob Bashara tells PEOPLE Day “was fine at her birthday party” which she celebrated in April.
“For her birthday event, she was in good spirits,” says Bashara. Shortly after, Day “developed a cough and it turned into bronchitis and she was briefly hospitalized,” he says.
“When she came home, she began to decline and was given hospice care,” he says.
“[When she died] there were some very close friends and loved ones who were with her,” says Bashara. “She was surrounded by a few loved ones.”
Bashara adds Day “died peacefully” after a fulfilling life working on films and TV shows.
“She lived by her most famous song, ‘Que Sera, Sera.’ That was her belief. Whatever will be, will be, and there is a purpose for everything that happens and you need to get on with her life,” explains Bashara. “She always looked forward and looked for the good in whatever happened.”
As for her multitude of fans, Bashara says Day knew she was beloved.
“She still gets so much mail and it’s reinforced from fans. Often they tell her how one of her movies uplifted them at a time when things were difficult,” he says. “It brought her great joy to know her songs or films helped people in her lives. That was the important thing to her.”
Despite receiving heartfelt appreciation from her fans, Day was “embarrassed to talk about herself or to receive accolades because she loved working.”
“She did it because she loved it and she had a God-given talent,” says Bashara. “And she said, ‘God gave me a voice and all I did was use it.'”
Day died at 1 a.m. on Monday at her home in California. The Associated Press was first to report the news, which comes nearly two months after the actress celebrated her birthday and shared a recent photo with PEOPLE.
By the early ‘60s, Day was the No. 1 box office star on the planet. As the ’60s wound down, Day turned to TV, having been forced there by a contract signed by late husband Melcher without her knowledge. CBS’s 1968-73 The Doris Day Show never rose above the level of being a poor man’s Mary Tyler Moore Show, and Day herself was highly critical of it.
For Day, as she told PEOPLE in 2011, her greatest loss in life was the 2004 death (from melanoma) of her son, music producer Terry Melcher.
“I had him when I was , so we were like sister and brother,” said Day, who found his passing “really hard. But I keep him with me.”
The profile also pointed out that humor had always been Day’s secret weapon. “I love to laugh,” said the star who made so many others laugh and sing. “It’s the only way to live. Enjoy each day — it’s not coming back again!”