 She first played Australian rules football at the age of six in Auskick clinics at the Logan City Cobras Football Club.Her first game of competitive football came that same year when she filled in for her older brother's under eights side, where she kicked seven goals on debut.Brennan continued to play with the Logan Cobras boys through to girls eligibility age cut-off at 15, including in one season where she won a club best and fairest award at under 14s level.