McKinnon was born in Melbourne, Victoria before moving to Sydney's North Shore at a young age playing soccer, netball and basketball there.[1] She gained an interest in the sport after watching her brother play Auskick.[1] When the club advertised for female players she joined at age 12, but there were not enough players to field a team.[1] McKinnon was part of the first Mosman Girls Youth team and after a few seens drew the attention of local recruiters due to height and athletic ability.[2]