Lippeatt began gymnastics in 2007.[1] Her first national competition was the 2015 HOPES Championships in Chicago, where she placed first on uneven bars and fifth all-around.[2]
In March 2017, Lippeatt competed at the Nastia Liukin Cup, placing first on floor exercise and beam, and seventh all-around.[3] That same month, Lilly went on and qualified as a Junior International Elite at KPAC Elite qualifier.[1] In July 2017 she competed at the US Classic, placing seventh on floor and tenth all-around.[4] She also competed at the 2017 P&G Championships. There Lippeatt ranked 15th all-around,[5] 25th on vault, 24th on uneven bars, 14th on balance beam and tenth on floor exercise.[6]
She joined the United States' junior national team on February 24, 2019.[8] In March 2019, she made her international debut at Gymnix International alongside fellow American juniors Skye Blakely, Olivia Greaves and Kaylen Morgan.[9] The American team won the junior team final.[10] Individually Lippeatt finished fifth all-around[10] and won bronze on balance beam.[11] In July 2019, she competed at the GK US Classic, placing ninth all-around.[12] At the US Gymnastics Championships in Kansas City that August, Lippeatt finished fifth on uneven bars and floor exercise,[13] and eighth all-around.[14] Lilly was named Region 5 Elite Athlete of the year September 2019.[2]
February 28, Lilly competed in the 2021 Winter Cup Senior Division. She had a great showing and tied for third on floor with Shilese Jones and finished up fourth all-around. This earned her a spot on the Senior National team for the second time.[17]
