Lavelle was born in Cincinnati, Ohio, to parents Marty and Janet, and was raised with three siblings, John, Nora and Mary.

[4] As part of a third-grade book report, Lavelle chose to write about professional soccer star Mia Hamm.

[10] During her college break in the summer of 2015, Lavelle played for the Seattle Sounders Women of the W-League, where she was named in the All-League Team.

[15] However, after suffering a hamstring injury in June while on international duty, Lavelle missed over two months and finished the season with only ten appearances as a rookie.

[19] Despite making only six appearances the following year due to international duty, scoring one goal and recording one assist, Lavelle was named to the 2019 NWSL Best XI in the end of the season awards.

[20] With the 2020 season affected by the COVID-19 pandemic, Lavelle took part in the 2020 NWSL Challenge Cup, making four appearances and scoring one goal as Washington finished second in the preliminary group but were eliminated in the first knockout round by Sky Blue FC on penalties.

She started in the November 2020 final against Everton, and Manchester City would end up winning the match 3–1 in added extra time.

[29] On May 17, 2021, OL Reign announced the return of Lavelle to the NWSL as an allocated player having acquired her playing rights prior to her move to England in August 2020.

[31] Lavelle missed the majority of the 2023 NWSL season due to injury and being rostered for the 2023 FIFA Women's World Cup.

[33] She was one of four national team players who joined Gotham as free agents that off-season along with Crystal Dunn, Tierna Davidson, and Emily Sonnett.

[34] After missing the start of the season due to a lower leg injury, she made her club debut on April 28, coming off the bench and scoring the tying goal in stoppage time to draw 1–1 against Racing Louisville.

[41] On June 4, 2024, Lavelle became the 43rd woman to appear in 100 matches for the U.S. Women's National Team, starting in a 3–0 victory over South Korea.

During the U.S. knockout round match against Spain, she drew a penalty kick that was converted by Megan Rapinoe to seal the team's 2–1 win and advance to the quarterfinals.

[52] Lavelle appeared in all six games as the team won the bronze medal, losing to Canada 1–0 in the semi-final before beating Australia 4–3 in the third-place playoff.

[54] Lavelle was named to the national team roster for the 2023 FIFA Women's World Cup, though she played limited minutes in the early stages of the tournament due to a knee injury.

[61] Lavelle was featured on the June 2023 cover of Sports Illustrated along with national teammates Alex Morgan, Trinity Rodman, and Sophia Smith.