She described the youngster as "the most caring, loving, happy girl that you could ever meet".
"She would always stick up for anyone around her as her motto was 'treat people how you want to be treated'. Unfortunately my baby sister had a secret she wouldn't tell anyone and that was that she was being bullied.
"She had so much to live for, she wanted to be a social worker and had an amazing voice once she got over her shyness. We were meant to be at her graduation and dance and give her away at her wedding. Most of all, she was meant to have a family of her own. She will now never get that chance because a bully does not realise how much their works and actions can really affect someone."
Ms Denoon said her sister's death had been the worst experience imaginable for their parents.
"What our parents have been through, I wouldn't wish on anyone. Our mother lost her baby girl and Kyana's father lost his only daughter, his pride and joy," she wrote.
She said up to 200 people attended her sister's funeral.
The Givealittle page, created to raise financial support for Kyana's parents, is now closed.
Grieving friends and family of the 12-year-old girl have posted moving tributes.
"RIP Beautiful girl Everyone's missing you so much I know you'll be watching over us as a beautiful angel," Alyssa Shailer wrote on Instagram.
Amelia wrote: "Miss you kyana Still pray for you xx."
Messages of condolence have also been posted alongside her death notice, which said, "It is with sadness in our hearts that we announce the passing of Kyana," who is described as a treasured daughter.
"Missing you so much Kyana, x Life is just not the same without you," wrote Kamia Pere.
"School is just not the same. I am missing you and thinking about every day. You spread your wings and fly high Beautiful xx"
Last year 564 people committed suicide in New Zealand, including 10 children between the ages of 10 and 14.
Under the Harmful Digital Communications Act, passed last year, it is an offence to send or publish threatening messages or material. Eight people have been charged by police under the act and one person was jailed for four months.
Where to get help:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• The Word
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• CASPER Suicide Prevention
If it is an emergency and you feel like you or someone else is at risk, call 111.
