Kate Spade's best friend says the designer felt 'deep sadness' before suicide

Elyce Arons didn’t realize the extent of her best friend Kate Spade‘s depression until it was too late.

Spade died by suicide in June at 55 years old, which came as a shock to Arons, who admitted she knew Spade was occasionally down, but never expected her to end her own life.

“It was tough because she didn’t always say [she was unhappy],” Arons, 55, told “Good Morning America” in an interview airing Thursday. “She’d be sad, and then one minute later she’d make a joke … We talked every day, and most of the time she was very happy. But I don’t know if anyone can understand the depths of depression of another person.”

Arons said she can’t quite fathom why Spade would have killed herself and thinks it was a spontaneously tragic choice.

“I have thought and thought and thought about it, and I think it was one moment of deep despair, of deep sadness that she felt when she was alone … and I can’t answer what that was,” she said.

Spade’s demons may have been hidden from Arons, but others apparently knew Spade’s struggle.

Spade’s estranged sister, Reta Saffo, alleged that Spade suffered from bipolar disorder, while fashion insiders claimed she had a drinking problem.

Her husband Andy said in a statement after her passing that she suffered from anxiety and depression “for many years” but denied that she had any substance abuse issues.

Arons and Spade met at the University of Kansas and founded the Kate Spade handbag label together in 1994.

After Spade sold her namesake brand in 2007, she and Arons launched Frances Valentine, named after Spade’s daughter and father’s side of her family.

Arons vowed to keep the brand and its small 10-person team going following Spade’s suicide.

“Katy had this need to create,” she said. “We’ve had a lot of people write in and talk about how she had changed their lives, and please keep going and please keep her designs alive, and that’s what we’re going to do. We miss her every day. Her spirit’s here.”

This article originally appeared in Page Six.