Spencer was born in Montreal, Quebec. Joining her older brothers, Spencer started training in Taekwondo at the age of four. At twelve years old, she started training in Brazilian jiu-jitsu and added kickboxing to her training five years later. She transitioned to train in MMA when she joined Jungle MMA in 2009, when she moved to Orlando to attend the University of Central Florida.
Spencer started her amateur career in 2012. After winning the first "Tuff-N-Uff Future Stars of MMA" tournament where she submitted Leanne Foster and knocked out Jessica Eve Richer at the second "Tuff-N-Uff Xtreme", amassing a record of 5–1, Invicta FC signed her in 2015.
Invicta Fighting Championships
Spencer made her promotional debut on September 12, 2015 at against Rachel Wiley. She won the fight via a technical knock out in round one. Her next fight came over eighteen months later on March 25, 2017 at. She faced Madison McElhaney in a Featherweight bout and she won the fight via unanimous decision with the scoreboard of. On July 15, 2017 Spencer faced Amy Coleman at. She won the fight via a rear-naked choke in round one. Spencer faced Akeel Al-Hameed on January 13, 2018 at. She won the fight via unanimous decision. Spencer faced Helena Kolesnyk on July 21, 2018 at. She won the fight via a rear-naked choke. Spencer faced Pam Sorenson on November 16, 2018 at for the vacant Invicta Featherweight title. She won the fight via a rear-naked choke in round four.
Spencer signed with the UFC in March 2019 after compiling an undefeated record of 6–0 competing in Invicta FC. Spencer made her promotional debut on May 18, 2019 at against Megan Anderson. Spencer won the fight in the first round by rear naked choke. Spencer faced Cris Cyborg in the co-main event on July 27, 2019 at UFC 240. She lost the fight via unanimous decision. Spencer faced Zarah Fairn Dos Santos on February 29, 2020 at UFC Fight Night 169. She would go on to win the fight via TKO in the first round. Spencer was expected to face current champion Amanda Nunes on May 9, 2020 at UFC 250. However, on April 9, Dana White, the president of UFC announced that this event was postponed and the bout eventually took place on June 6, 2020 at UFC 250. She lost the bout via unanimous decision.
