"She was being bullied the entire school year, with words such as 'kill yourself,' 'you think you're white because you ride with that white boy,' 'you ugly,' 'black b***h,' 'just die,'" she told the newspaper.
Her aunt, who is a television host in Atlanta, wants to use her platform to denounce bullying in the hope of preventing other families from experiencing the same tragedy.
"God has blessed me to help others with my platform, and now it's time to help. There are so many voiceless kids," she said.
"God is opening great doors for justice for my niece."
Where to get help:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• Samaritans 0800 726 666
• If it is an emergency and you feel like you or someone else is at risk, call 111.