Nighswonger played youth soccer for Slammers FC, winning a U14 ECNL National Championship.

[26] The Atlantic Coast Conference named Nighswonger the most valuable player of the 2022 ACC women's soccer tournament.

[28] In November 2022, Nighswonger said she was eschewing the fifth year of NCAA eligibility granted by the association due to the COVID-19 pandemic and considering playing for a European club after finishing her career at Florida State.

[40] The NWSL named Nighswonger its Rookie of the Month in May and July, making her the only player to earn the award twice.

[45][46] She made her debut for Arsenal in their Women's FA Cup match against London City Lionesses on February 9, participating in their 2–0 victory.

[51] She was called into her first full women's national team camp November 20, 2023 and made her first appearance on December 2, 2023, in a 3–0 win against China PR.

[54] She scored her first goal on February 20, 2024, when she converted a penalty against the Dominican Republic during the 2024 CONCACAF W Gold Cup.

[57] In 2022, Nighswonger donated $1,000 to the Breast Cancer Research Foundation, using money from her name, image, and likeness deal with Garnet & Gold.