Kate Spade's apparent suicide ''wasn't unexpected'' by her family.

The 55-year-old fashion designer is believed to have taken her own life at her New York apartment on Tuesday (05.06.18) and her older sister, Reta Saffo, has now told how her sibling suffered from debilitating bipolar disorder for the last three or four years and had been self-medicating with alcohol.

Reta claimed to have tried for a long time to persuade Kate to seek help but her sister was concerned hospitalisation could harm the image of her ''happy-go-lucky'' eponymous fashion brand.

She wrote in an email to the Kansas City Star newspaper: ''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 hospitalization). She was always a very excitable little girl and I felt all the stress/pressure of her brand (KS) may have flipped the switch where she eventually became full-on manic depressive...

''I'd come so VERY close to getting her to go in for treatment (to the same place Catherine Zeta-Jones went for her successful bipolar treatment program). I'd spoken with them on the phone (not telling them exactly who the patient would be). They agreed to fly in and talk with her and take her with them to the treatment center.

''She was all set to go -- but then chickened out by morning. I even said I (would) go with her and be a 'patient' too (she liked that idea) I said we could talk about it all -- our childhood, etc. That I could help her fill in any blanks she might have . . . .

''That seemed to make her more comfortable, and 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. She was definitely worried about what people would say if they found out. (sic)''

Kate's husband and business partner, Andy Spade - the father of her 13-year-old daughter Frances Beatrix, who is known as Bea - also tried to persuade his wife to be admitted for treatment and helped to make plans on how it could work, but ''nothing ever came of it''.

And Reta thinks Kate ''perhaps had a plan'' for ending her own life.

She wrote: ''After numerous attempts, I finally let go. Sometimes you simply cannot SAVE people from themselves! One of the last things she said to me was, 'Reta, I know you hate funerals and don't attend them, but for me would you PLEASE come to MINE, at least. Please!'

''I know she perhaps had a plan, but she insisted she did not.(sic)''

The 57 year old recalled how Kate grew obsessed with Robin Williams' 2014 suicide, after seeing a report on his death while in a hotel in Santa Fe.

She said: ''We were freaked out/saddened, but she kept watching it and watching it over and over. I think the plan was already in motion even as far back as then.''

Reta ended her email with a short tribute to her sibling.

She wrote: ''She was a dear little person. So dear -- so kind, so funny. I'll miss our 6-7-hr-long phone conversations between NY and NM.

''I'm off to bed for a good cry.''