[5] With the COVID-19 pandemic resulting in the cancellation of the international junior season, Thorngren's lone major appearance was in making her domestic senior debut at the 2021 U.S. Championships.

Due to French travel rules, Russian women's skaters who normally dominated the Junior Grand Prix could not participate in the event.

"[8] At her second event, the 2021 JGP Slovenia, Thorngren won the bronze medal behind Russians Adeliia Petrosian and Sofia Samodelkina.

[5] Hoping to qualify for the American Olympic team at the 2022 U.S. Championships, Thorngren was fifth in the short program with a clean skate, only 1.20 points behind third-place Alysa Liu.

[12] As Russian women had dominated international figure skating in recent years, this had a significant impact on the field, and Thorngren was considered a medal contender.

[13] Due to both the invasion and the Omicron variant, the World Junior Championships could not be held as scheduled in Sofia in early March, and were rescheduled for mid-April in Tallinn.

[16] Standing on the podium alongside fellow American, Isabeau Levito, she concurred that "the medal is a reflection of our training and how hard we've worked this season, and I'm really happy.

[17] Thorngren was invited to make her Grand Prix debut at the 2022 Skate Canada International, placing ninth of twelve skaters.

[18] She finished fourth in the short program at her second event, the 2022 Grand Prix of Espoo, but dropped to sixth place after the free skate.

[20] Recovering in time to appear on the Grand Prix at the 2023 Skate Canada International, Thorngren finished fifth in the short program despite underrotating the second half of her jump combination.

[21][20] At her second assignment, the 2023 NHK Trophy, Thorngren sprained her ankle in practice before the short program, but won the segment by a margin of 5.49 points over Belgian Nina Pinzarrone.

In the free skate she doubled and fell on a planned triple Salchow and again received a flip edge call and a time violation.