Grant-Mestis played four years of NCAA Division I ice hockey with the Merrimack Warriors of Merrimack College, a member institution of the Hockey East conference, located in North Andover, Massachusetts. On November 8 of her senior season, she had a four-point (two goals, two assists) game against Maine, becoming just the second player to surpass 100 points in Merrimack program history. She went on to score a hat-trick against Brown three weeks later and was recognized as the Hockey East Co-Player of the Month for November 2020. Her season totals distinguished her as the Warriors' leader in goals (20) and points (33), ranking second on the Hockey East goals leaderboard and top-10 in scoring nationally. In total, she scored 117 points (56 goals and 61 assists) in 137 games with the Warriors and is the program's all-time leading point scorer, all-time assists leader, and second all-time in goals
At the end of February 2020, Grant-Mentis signed with the Buffalo Beauts to finish the 2019–20 NWHL season along with Merrimack teammate Léa-Kristine Demers. She scored three points (2+1) in two regular season games and added another two points (1+1) in the NWHL playoffs semi-final qualification as the Beauts lost to the Connecticut Whale. She was named Player of the Week in her first week in the NWHL.
In May 2020, she signed with the Toronto Six, joining the team ahead of their first season in the NWHL. Her first NWHL goal took place in a January 24, 2021, contest versus the 2019 Clarkson Cup champion Minnesota Whitecaps.  A 6–5 shootout loss, Grant-Mentis became the only Six player to score in the shootout round. She recorded the game-winning goal in the Six's first win in franchise history against the Boston Pride on January 26, coming back from a 1–0 deficit with a pair of third period goals by Brooke Boquist and Grant-Mentis. She become the most decorated player in a single NWHL season, earning a record four accolades, including the first black player in league history to win the Most Valuable Player and Newcomer of the Year Award. Additionally, she was the leading scorer on the Six, which won the regular season title, and was tied as the league-leading scorer.
We are very excited to have her apart of the Sport Displays team and we will have some more exciting news coming up shortly to share with you all!