O'Connor, of Durham in the UK, revealed she had ulcerative colitis last year, sharing her story in the hope of helping others.
A decorated amateur, O'Connor won gold at the 2017 Commonwealth Youth Games. She was 3-0 as a professional after making her debut in 2021.
O'Connor's promoter Ben Shalom said the news was heartbreaking.
Shalom said on social media as cited by Sports Central: "It's hard to make sense of this. "A lot goes on in life but nothing else matters other than your family and your health. "My heart goes out to Georgia's parents and partner, who I know did everything they could tirelessly and are going through so much right now. "Georgia was an inspirational person and one I'll never forget. So sorry for her family and all her friends. Truly heartbreaking."
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