Lee fought under the Singapore and US flags and ONE’s youngest world champion at 19 when she claimed the inaugural women’s Atomweight World Championship in May 2016.
Her brother Christian Lee and her have been in hiatus since their sister’s death.
With her retirement, Lee’s focus will turn to her budding non-profit organisation Fightstory, which she set up in March this year.
Last week, she revealed a car crash in 2017 was not an accident but a suicide attempt.
In an interview with CNA during her first trip back to Singapore since Victoria’s death, she spoke openly about her own mental health struggles and paid tribute to her sister.
“Whether you’re a fighter in the cage, or you’re a teacher or a doctor or a stay-at-home mum, we’re all fighters in our own way,” she said.