Montreal native Fernandez boasts a multicultural upbringing, with fluency in English, French, and Spanish. Commencing tennis at five and competition at ten, she also delved into volleyball, soccer, and track and field. Despite a setback at seven, when Tennis Quebec's development scheme declined her, Fernandez's coach Jorge saw potential. Armed with tennis literature and videos, he drew from his soccer background to hone her speed and agility, countering her petite stature. At 5-foot-6, Jorge became her caregiver as her mother pursued work in California. The family resettled in Florida when she was twelve, granting her year-round tennis access. A stint at Tennis Canada National Training Center marked her teen years. Electing her international allegiance was no easy feat. Ecuador flirted briefly as an option, but loyalty to Canada, her birthplace, and the roots of her family led to Fernandez's decision. Back on January 25, 2019, a determined and youthful Fernandez stepped onto the grand stage of the Australian Open girls' singles final. At just 16 years old, Fernandez displayed her remarkable talent and spirit, although she faced a formidable challenge in the form of the top-seeded Clara Tauson, resulting in a closely contested match that ended in Tauson's favor. Undeterred by this setback, Fernandez continued to rise in the tennis world, and her moment of triumph arrived on June 8, 2019, at the revered grounds of Roland Garros. In an exhilarating showdown, she outplayed Emma Navarro in the French Open final, etching her name in the annals of history as the first Canadian female player to clinch a junior Grand Slam title since Eugenie Bouchard's triumph at the 2012 Wimbledon Championships. Switching to the senior tour, Fernandez rose to No. 371 globally. Her debut Women’s Tennis Association (WTA) win arrived at Quebec City's National Bank Cup on September 10, 2018. In 2019, Fernandez entered WTA contests in Canada and Japan, exiting in round one each time. Still, she seized singles and doubles titles at the National Bank Challenger in Gatineau, Quebec. 2020 marked a turning point as Fernandez secured three Grand Slam victories. She overcame two-time finalist Vera Zvonareva at the US Open's onset. Subsequently, she conquered Magda Linette, and Polona Hercog during the French Open's initial rounds. By year-end, Fernandez held the world No. 88 rank. In 2021, Fernandez's triumphs continued. She commenced with a commanding win against 2017 US Open champion Sloane Stephens at the Grampians Trophy in Melbourne. Then, she clinched her inaugural WTA title in Monterrey, Mexico, by defeating Viktorija Golubic in the final. The 2021 US Open saw Fernandez's spectacular wins. After triumphing over Ana Konjuh in round one and Kaia Kanepi in round two, Fernandez faced Naomi Osaka. In a gripping encounter, Fernandez secured a victory. The victories continued as she beat Angelique Kerber, Elina Svitolina, and Aryna Sabalenka. Despite a loss to Emma Raducanu in the final, Fernandez ended 2021 with a 25–17 record and the world No. 24 ranking. Her accomplishments led to Canada's Bobbie Rosenfeld Award. In 2022, Fernandez defended her Monterrey title, defeating Camila Osorio. Impressing at a Billie Jean Cup match, she propelled Canada to the finals, scheduled for November 2022.