She attended the English Martyrs School,[3] where she achieved 12 GCSEs before gaining a Distinction in a BTEC National Diploma in Sport at Hartlepool College.

[4][5] She began boxing aged 12,[6] when she joined a local Hartlepool Headland club after seeing a boy showing off his trophy on the street and decided she wanted one.

She stated that she thinks the trainer looked at her as 'an annoying little girl who kept on coming back' but she was determined, having fallen in love with the sport.

[9] At the 2014 Commonwealth Games in Glasgow, Marshall beat Ariane Fortin of Canada to take the gold medal in the women's middleweight division.

[22] Marshall lifted the vacant WBA super-middleweight Inter-continental title in Sofia, Bulgaria, after winning all 10 rounds to claim a comfortable points victory over Yanina Orozco of Argentina.

[23] On 31 October 2020, in her ninth professional fight, Marshall became the WBO female middleweight world champion with a TKO victory over Hannah Rankin at Wembley Arena.

[29] Marshall challenged Franchón Crews-Dezurn for her undisputed super-middleweight world titles in the main event at the Manchester Arena on 1 July 2023 winning by majority decision.