Betty White recorded a "tribute" to her fans just 10 days before she died aged 99. 

The Golden Girls legend had collaborated producer Steve Boettcher - who had been working on the pending special Betty White: A Celebration to mark what would have been her 100th birthday on January 17 - and she filmed a message for her fans on December 20, just a week and a half before her death on New Year's Eve. 

He told Entertainment Tonight: "On December 20, she did a short little video for us... it was kind of a tribute to her fans that were going to be with her at the event. It's kind of a shout-out to her fans that she did 10 days before she passed away." 

According to Boettcher, the Mary Tyler Moore Show star "looked amazing" in the video and he gushed about how much the five-time Emmy Award-winner adored "getting glammed up". 

He shared: "She looked amazing, she loved getting 'glammed up,' as she calls it, in her hair, makeup, she was just striking and beautiful. She was smiling and really she wanted to thank her fans sincerely, from the bottom of her heart, for all the support over the years." 

Betty White died aged 99 of 'natural causes' according to reports. Photo / AP 

Boettcher also said she "was just living her best life, and that's what we want for Betty White" before her sad death. 

Despite her passing, the documentary will still be debuting on what would have been her 100th birthday and show how she was "happy" and "the eternal optimist". 

Boettcher added: "I think just that she was happy and the eternal optimist. 

"You'll see that in the movie coming out on the 17th of January, that she has this unbelievable look at life and view of life and that it just rains through her entire career and her personal life. [She was] just the eternal optimist." 

Boettcher revealed that the film will show The Proposal star in her personal life and in more intimate "quiet moments", while it will also feature contributors such as Ryan Reynolds, Tina Fey, Robert Redford, Lin-Manuel Miranda, Clint Eastwood, Carol Burnett, Jimmy Kimmell and Craig Ferguson.