Mavor was born in Glasgow but grew up in Canonmills, Edinburgh, after moving there with her parents and older brother Alex. Her father James Mavor is an award-winning playwright who heads up the MA screen-writing course at Napier University. Her grandfather, Ronald Bingo Mavor, was The Scotsman's theatre critic in the early 1960s before he became the director of the Scottish Arts Council.Mavor declared she first became interested in acting after watching The Shining when she was 10 years old.She studied at Mary Erskine School in Edinburgh and is a member of the National Youth Theatre.Mavor made her professional debut in 2011, when she gained a lead role as Mini McGuinness in the fifth and sixth series of E4 BAFTA-winning drama Skins. She described her character as "quite a feisty and witty figure, but she doesn't really think about the consequences of her actions." Freya assured that in reality she couldn't be more different to her on-screen character.Mavor was enlisted as the face of Pringle of Scotland for its 2011 spring/summer campaign. She also won the Fashion Icon of the Year Award at the 2011 Scottish Fashion Awards.