In her youth, Macfarlane played basketball, but her aspirations in the sport came to a stop due to series of knee injuries. Macfarlane graduated Punahou School in 2009 in Honolulu, Hawaii. Although she got a scholarship for wrestling to Menlo College, she decided to study Anthropology at San Diego State University from where she earned Bachelor Degree in 2013. After earning her Bachelor Degree in 2013, she continued her education at SDSU to study Master of Arts in Liberal Studies. During the summer before grad program, she decided to lose some weight she gained in the college and joined a CrossFit gym and Liz Carmouche's MMA gym. She grew affinity for mixed martial arts and continued training at the San Diego Combat Academy.
Macfarlane began her amateur MMA career in 2014. She fought five times during that year, mainly with Xplode Fight Series, and went undefeated as an amateur. Macfarlane's first professional fight was an unsanctioned match against Katie Castro for Xplode Fight Series in 2015. Macfarlane won via technical knockout ten seconds into the bout. In the aftermath of the lopsided affair, the California State Athletic Commission launched an investigation into the organization's unsanctioned MMA events. Castro had a 0-2 record before fighting Macfarlane and footage of the match was posted on the internet and labeled "Soccer mom loses to MMA fighter". The video went viral, garnering over a million views on YouTube and was discussed on a few television news networks.
Bellator MMA
Following the bout with Castro, Macfarlane signed a three-fight contract with Bellator MMA. She made her debut in August 2015 at Bellator 141 where she defeated Maria Rios by split decision. Macfarlane fought Amber Tackett at Bellator 148 where Macfarlane won by armbar submission in the first round. Macfarlane's next bout was against Rebecca Ruth at Bellator 157 where she won by standing rear-naked choke in the second round. Macfarlane would then fight Emily Ducote at Bellator 167 where she was victorious via unanimous decision. Macfarlane faced Jessica Middleton at Bellator 178 and won by armbar submission in the first round. Macfarlane and Emily Ducote had a rematch at Bellator 186 for the inaugural Bellator Women's Flyweight World Championship. Macfarlane won the bout with an armbar variation in the fifth round to win her first MMA championship. Macfarlane faced Alejandra Lara at Bellator 201 for the first defense of her flyweight title. Macfarlane won the fight in the third round via armbar. Macfarlane faced Valérie Létourneau at Bellator 213 in Macfarlane's hometown of Honolulu, Hawaii. Macfarlane successfully defended her title for a second time, defeating Létourneau by third round submission. In her third title defense, Macfarlane faced Veta Arteaga at Bellator 220 on April 27, 2019. She won the fight via TKO due to a doctor's stoppage in the third round. Macfarlane made her fourth title defense against Kate Jackson at Bellator 236 on December 21, 2019. Macfarlane was victorious via unanimous decision. On February 10, 2020, it was announced that Macfarlane had signed a ten-fight, five-year extension contract with Bellator.
