Johnson was raised in Altamonte Springs, Florida and competed collegiately for the Oklahoma State University.

[4] In 2021, she left Bowerman to join the Nike Union Athletics Club under coach Pete Julian.

Competing at the 2018 Big 12 Cross Country Championships, Johnson finished with a runner up performance in Ames, Iowa.

In August 2019, Johnson announced her intention to turn professional, forgoing her final season of collegiate eligibility at OSU, and joining the Bowerman Track Club under coach Jerry Schumacher shortly thereafter.

Sinclaire opened her 2023 season winning a 800–1500 m double in the professional races at Nike Outdoor Nationals.

At the USA Championships, Johnson aimed to defend her 1500 m national title, but just missed the podium, placing fourth in 4:03.49.

The following week, on September 16, she competed in the Diamond League Final held at the Prefontaine Classic, placing 12th in 4:03.21.