Lieutenant Colonel Costello was commissioned into the Australian Army in 2002 and has undertaken a diverse range of clinical, organisational, operational, command and staff appointments during her service. Lieutenant Colonel Costello holds a Masters Degree in Organisational Psychology and currently leads the Human Performance Optimisation team at Headquarters Forces Command. She has served as the Officer-in-Charge of the ADF Centre for Mental Health, as the Senior Psychologist in the Commander’s Advisory Group at Forces Command, and prior to her current appointment, as the Commanding Officer of the 1st Psychology Unit.