Mabli was a medic aboard the Tsuranga hospital ship. She was only on her second tour of duty when she and her fellow medic Astos picked up the Thirteenth Doctor, Graham O'Brien, Ryan Sinclair and Yasmin Khan.
Mabli's inexperience comes into play when she is easily threatened by Ronan into ingoring her Hippocratic Oath and providing an excessive amount of Adrenaline blockers to Eve Cicero; when her faked Corden Fever would be negatively affected. (TV: The Tsuranga Conundrum)