KATE Spade’s sister said that the fashion designer suffered from mental illness for years but refused treatment because she was concerned it would impact her brand.

The 55-year-old was found dead inside her Upper East Side apartment in New York.

Ms Spade, who built an empire on her famous handbags before branching out into other accessories, was reportedly found in her bedroom by a housekeeper around 11am (1am AEST).

Police said the death was not suspicious.

In an email to The Kansas City Star, Kate’s older sister Reta Saffo said news of Ms Spade’s sudden death was “not unexpected”.

“I will say this was not unexpected by me. I’d flown out to Napa and NYC several times in the past 3-4 years to help her to get the treatment she needed (inpatient hospitalisation),” Ms Saffo wrote.

She said she had “gotten very close to getting her to go” to a rehab facility for treatment, but Ms Spade “chickened out”.

“...We’d get sooo close to packing her bags, but — in the end, the ‘image’ of her brand (happy-go-lucky Kate Spade) was more important for her to keep up,” Ms Saffo said. “She was definitely worried about what people would say if they found out.”

After several attempts she said she gave up. “Sometimes you simply cannot SAVE people from themselves!” she wrote.

“She was a dear little person. So dear — so kind, so funny. I’ll miss our 6-7-hr-long phone conversations.”

She also revealed that Ms Spade made her promise to attend her funeral and that she was fixated with Robin Williams’ death back in 2014.

FAMILY AND FRIENDS IN MOURNING
Meanwhile, Ms Spade’s brother-in-law, actor David Spade, took to Twitter to share a special memory of Ms Spade and remind people that life can be a struggle.

The SNL and Just Shoot Me star is the brother of Kate’s husband Andy.

“Katy at my book signing. I love this pic of her. So pretty. I don’t think everyone knew how f—king funny she was. Its (sic) a rough would out there people. Try to hang on,” he wrote.

He shared another image on Instagram of them at Christmas time, saying “We had so much fun that day. She was so sharp and quick on her feet. She could make me laugh so hard. I still can’t believe it.”

David Spade was spotted in Los Angeles where he was being consoled by a friend following the tragic news.

The family issued a statement to the New York Daily News that read, “We are all devastated by today’s tragedy. We loved Kate dearly and will miss her terribly. We would ask that our privacy be respected as we grieve during this very difficult time.”

Ms Spade’s other sister Eve Brosnahan declined to give an interview to the news outlet saying, “It’s very difficult. I can’t right now. I just can’t.”

KATE’S MESSAGE TO HER DAUGHTER
Police said Ms Spade wrote a note, which sources claim was addressed to her 13-year-old daughter Frances Beatrix Spade.

The note, which TMZ reports was found near her body, is said by law enforcement to have read: “Bea — I have always loved you. This is not your fault. Ask Daddy!”

The designer’s husband, Andy, was home when her body was discovered, according to an AP report. Frances was at school.

According to the New York Post, a police source said relationship problems may have played a part.

“It was over family problems … in her relationship,” the source said.

According to entertainment website The Blast, Andy had been apartment hunting in recent months and was looking to buy a new pad in New York City.

NYPD Chief of Detectives Dermot Shea answered questions about her death at an unrelated press conference.

“At this point, there was a note left. The contents of that note, as well as the physical state of the apartment and the comments of the witness, lend to the credibility that it is an apparent suicide,” he said.

BUILDING AN EMPIRE
Ms Spade was born Kate Brosnahan in Kansas City, Missouri.

She earned a journalism degree before working in the accessories department of Mademoiselle magazine in New York.

In 1994 she started the fashion brand Kate Spade Handbags, which went on to become a global empire. It became one of the biggest names in female accessories, worn by stars including the Duchess of Cambridge, Anne Hathaway and Anna Kendrick.

She met her husband at university while working in a clothing store.

Ms Spade was the aunt of House of Cards and The Marvellous Mrs Maisel star Rachel Brosnahan.

Despite her meteoric success, she sold her firm in 2007 to spend more time with her daughter, according to TMZ.

It was eventually sold to Liz Claiborne Inc for $US124 million ($A162 million) and in May last year, Coach Inc bought it for $US2.4 billion ($A3.1 billion).

Spade got back into the fashion game in 2016, launching the luxury footwear and accessory brand Frances Valentine.

There were more than 140 Kate Spade New York outlets in the US alone, and more than 175 worldwide.

KENNETH COLE SLAMMED FOR TWEET
One of Kate Spade’s peers, designer Kenneth Cole, received backlash over a tone-deaf tweet about Ms Spade.

In the since-deleted tweet, he wrote: “‘I believed that I could, so I did’. She alone didn’t change the handbag world but she was an inspiring accessory. #KateSpade #RIP”

Twitter users were quick to react, slamming the “inspiring accessory” comment as rude and disrespectful.

“I’m boycotting @mr_kennethcole Extremely rude ‘inspiring accessory’ remark regarding #KateSpade #RIP” one woman wrote.

“I am stunned. Seriously? I wish I could say I’ll never wear your line again, but I NEVER bought that c—p in the first place. Kate Spade changed EVERYTHING,” another Kate Spade fan wrote.

While another tweeted: “Shame on you Kenneth Cole. The damage is done. I will not be supporting your brand again.”

Mr Cole tried to clarify what he meant in a statement, saying the he often says “We may not heel the world, but we hope to be an accessory”, purposefully playing on the word “heal”.

“After posting the tweet, I realised there may have been room for misinterpretation.”

Mr Cole replaced the offensive tweet with one that read: “Kate Spade left an indelible mark on the fashion industry and her inspiring life and work will be missed. We lost a true visionary today. My heart goes out to her family and to all she has touched.”

THE WORLD REACTS
Tributes have poured in for the designer from both inside the fashion world and the wider community.

If you are experiencing mental health issues or suicidal feelings contact Lifeline on 13 11 14 or BeyondBlue 1300 224 636. If it is an emergency please call 000.