[2] Hartley came through the youth ranks of hometown team Burnley and local rivals Blackburn before joining Manchester United's Centre of Excellence aged 13.

[1] Hartley made her senior debut and only appearance for Liverpool on 18 February 2018, in a Women's FA Cup fifth round tie against Chichester City.

[4] She was also one of nine players to have played alongside Casey Stoney, who was set to undertake her first managerial role as Manchester United W.F.C.

On 23 September, Hartley made her debut for the club when appearing as a 75th-minute substitute in a league game against London Bees.

[8] She made her debut in their opening game on 18 August 2019, playing the full 90 minutes in a 3–2 away loss against Aston Villa.