[3] Dempsey was trained in Joan Littlewood improvisation style as part of the junior group at Theatre Royal Stratford East.
[4] In 2014, she appeared as Vicky for ten episodes of the Ricky Gervais comedy series Derek.
[3] In 2019, she appeared in After Life,[8] then in 2020, she played a lead role as Emily Lacey in the TV series Harlots,[9] alongside Samantha Morton.
[8] In 2021 Dempsey played the role of Grace Melbury in a BBC Radio 4 adaptation of the Thomas Hardy novel The Woodlanders.
In 2022 and 2023 she took the lead role of Jess in three series of Matthew Broughton’s radio thriller Broken Colours.