Kaylei was born on July 4, 2003 in New York to Sherman and Onika McDonald. She has a brother, Zefanyah and a yorkie named Porscha. She was a member of National Language Honor Society, National Society of High School Scholars (NSHSS), Valley Stream South Varsity Gymnastics Team (Captain), Valley Stream South Varsity Track & Field Team and Valley Stream South Step Squad. She was given Gymnastics All American Award in 2019.

Valley Stream South's Kaylei McDonald an all-around force

When Kaylei was eight years old, she wanted to try a new sport and asked her parents if she could try gymnastics. She started taking recreational gymnastics classes for fun at a local gym in Cedarhurst, NY. Not long after, she joined pre-team and began competing level 4 in 2013. She placed third in the all-around and first on floor exercise at the 2016 Level 6 State Championships and fifth on floor exercise at the 2016 Level 7 State Championships.

In 2017, Kaylei qualified to the 2017 Level 8 State Championships and placed second on balance beam at the 2018 Level 8 State Championships. She moved up to level 9 for the 2019 season where she placed ninth on floor exercise at the State Championships. She qualified to the 2020 Level 9 State Championships but was unable to compete due to COVID-19 pandemic. Kaylei has been a NYSPHSAA Section 8 State Gymnastics Team Member for three years.