In June 2015, it was announced that Mullally would be the next bishop of Crediton, a suffragan bishop in the Diocese of Exeter. On 22 July 2015, she was consecrated a bishop by Justin Welby, the archbishop of Canterbury, at Canterbury Cathedral.
In June 2015, it was announced that Mullally would take on the position of bishop of Crediton, an auxiliary bishop in the Diocese of Exeter. On July 22, 2015, she was consecrated as a bishop by Justin Welby, the archbishop of Canterbury, at Canterbury Cathedral.