Hernandez was first added to the U.S. gymnastics national team in 2013 and began competing in international competitions that same year.

Outside of gymnastics, Hernandez has appeared on season 23 of Dancing with the Stars in 2016, where she won the competition along with partner Valentin Chmerkovskiy.

Hernandez hosted the first season of American Ninja Warrior Junior as the on-course reporter and starred as Valeria in the Nickelodeon animated miniseries Middle School Moguls.

[17] At the National Championships in August, she won the silver medal in the junior all-around competition with a total score of 116.650, behind Bailie Key.

[20] In November, she competed at the International Junior Mexican Cup in Acapulco alongside Bailie Key, Veronica Hults, and Emily Gaskins, and they won the team gold medal.

[26] In the junior-division event finals, she earned additional gold medals on the uneven bars and the floor exercise.

[27] At the U.S. Classic in July, she won the junior all-around title with a score of 58.450, as well as winning vault and uneven bars.

[30] Hernandez made her senior debut in 2016 at the City of Jesolo Trophy, where the U.S. team won the gold medal.

She contributed an all-around score of 59.800 toward the American team's first-place finish and placed third individually behind Biles and Raisman, but did not earn the all-around bronze medal because of a rule limiting medals to two gymnasts per country (Japan's Nagi Kajita took bronze instead).

[38] She placed third on uneven bars and balance beam and tied for third on floor exercise with MyKayla Skinner.

[53] She continued appearing on television and in the media throughout the next four years, as a show host and voice actor as well as a celebrity guest.

[58] In January 2020, Hernandez said that she was focusing on meets beginning in late May 2020: the U.S. Classic, U.S. Championships, and U.S. Olympic Trials.

[60][59] As the February camp was a selection for spring international meets, Hernandez could not participate in competitions held in March and April 2020.

[61] On April 29, Hernandez's former coach Maggie Haney was suspended by USA Gymnastics for eight years due to abusive conduct.

[62] Hernandez testified against Haney at the USA Gymnastics hearing,[62] and posted a message about her experiences on her social media without naming the coach.

[66] In February, Hernandez returned to elite gymnastics competition at the 2021 Winter Cup, competing on two events.

[77][78] In November 2017, Hernandez returned to the 25th season in week eight, to participate in a trio jive with Victoria Arlen and Chmerkovskiy.

[91][92] In 2019, she starred with Daniella Perkins and Jade Pettyjohn in the Nickelodeon animated mini-series Middle School Moguls, voicing a character named Valeria.

[72] She guest starred as herself alongside Dominique Dawes and Gabby Douglas in an episode airing in 2023 of the second season of the Disney+ animated series The Proud Family: Louder and Prouder.

[95] Hernandez provided color commentary for NBC's live daytime coverage of the women's artistic gymnastics events at the 2024 Summer Olympics.

[96][97] She discussed having imposter syndrome before the 2024 Summer Olympics and was praised for "her enthusiastic, insightful and down-to-earth" commentary.

[98] On November 24, 2016, she appeared on the 90th anniversary of the Macy's Thanksgiving Day Parade, riding the Spirit of America float.