[4] She studied history and French at the University of Sussex and graduated with a Bachelor of Arts (BA) degree in 1981.

In 1991, she moved to London to start a PhD, and to work as a medical sociologist and "ethno-cultural mental health research scientist".

[7] Before ordination in the Church of England, she was a research sociologist and academic, specialising in international development and ethno-cultural mental health.

[14] On 3 May 2022, it was announced that Mallett had been appointed as the next Bishop of Croydon, succeeding the Rt Revd Jonathan Clark on his retirement.

[5] In November 2023, she was one of 44 Church of England bishops who signed an open letter supporting the use of the Prayers of Love and Faith (i.e. blessings for same-sex couples) and called for "Guidance being issued without delay that includes the removal of all restrictions on clergy entering same-sex civil marriages, and on bishops ordaining and licensing such clergy".