Brantmeier began playing college tennis for the
North Carolina Tar Heels in the spring of 2023. She did not play in the fall of 2022 to avoid being ruled ineligible by the NCAA for collecting prize money during high school; she later filed suit against the NCAA over the rule. At the
2023 NCAA Championships, Brantmeier helped North Carolina win their first national team title. Playing in the team's No. 1 spot in place of
Fiona Crawley, she beat multiple ranked players during their run, including national No. 3
Lea Ma of
Georgia in the semifinals. Though she lost to
North Carolina State standout
Diana Shnaider in her singles match in the final, she and
Reilly Tran won the deciding doubles match that gave North Carolina an early 1–0 lead. Brantmeier additionally reached the NCAA doubles tournament final with
Elizabeth Scotty, losing to North Carolina teammates Crawley and
Carson Tanguilig. , 2025, Master'U Brantmeier swept the
Intercollegiate Tennis Association (ITA) Fall National Championships in the fall of 2023, winning national titles in singles and doubles with Scotty. In the spring of 2024, she
tore her meniscus during the ITA National Team Indoor Championship, ruling her out for the season. ==ITF Circuit finals==