Allen started playing football in Ashton Keynes, Wiltshire when she was 5 and coached by her father.[4] She later moved to Swindon Town Ladies followed by Swindon Badgers before joining Cirencester Town F.C. in Gloucestershire. In 2008, when she turned 16, Allen signed a contract with FA Women's Premier League National Division team Bristol Academy W.F.C. as she was unable to sign a contract until then.[5] In 2010, she was part of the Filton Academy team that reached the final of the English Schools Cup when she was 18. Later in the year, Allen made her first team debut for Bristol Academy coming on as a substitute against Everton Ladies in the FA Women's Premier League National Division.[4] Allen then joined Cardiff Met. Ladies in 2011.[3] While playing for Cardiff, in 2013, Allen set a Welsh Premier Women's Football League record by scoring 15 goals in one game against Caerphilly Castle F.C.[6] In 2015, Allen played for Cardiff Met. Ladies in the UEFA Women's Champions League and scored the team's only goal in the campaign.[2] She was later named as the team captain,[7] and also took the team's penalty kicks.[8] In 2021 she rejoined Cardiff Met.[9]