Miller attended Franklin High School in Somerset, New Jersey, where she was rated a five-star recruit by ESPN and earned McDonald's All-American honors in 2019.

[6] In her sophomore season, Miller averaged 18.1 points, 6.6 rebounds and 3.8 blocks per game,[2] leading Franklin to a New Jersey Tournament of Champions and Group 4 state titles.

[7][8] As a junior, Miller averaged 23.8 points, 7.7 rebounds, 3.8 assists and 3.8 blocks per game, and was named Courier News Player of the Year for 2018.

She broke her own program single-season scoring record and surpassed her sister, Adreana, as Franklin's all-time leading scorer.

[9] Miller led her team to the Group 4 state championship, scoring 27 points against Toms River High School North in the title game.

[10] In her senior season in 2018–19, she averaged 21.8 points, 8.7 rebounds and 3.1 blocks per game, repeating as Courier News Player of the Year.

[17] She received her first college basketball scholarship offer from Villanova, her father's alma mater, in eighth grade.

[27] She scored 24 points, with nine rebounds, three assists and three steals, in an 89–65 win over Florida Gulf Coast at the second round of the 2022 NCAA tournament.

[35] As a senior, Miller averaged 19.7 points, 6.6 rebounds, 2.9 assists and 2.1 steals per game, and set the program single-season record with 201 free throws made.

[39] In the July 26, 2023, Lynx home game against the Washington Mystics, she became the first WNBA rookie to ever score 20 or more points (she had 21), have 9 or more assists, and only have 1 or no turnovers.

[42] In her rookie year, Miller became the third Lynx player to tally "at least 380 points, 110 rebounds, 30 steals and 10 blocks, joining Napheesa Collier (2019) and Maya Moore (2011) to achieve this feat.

[4] She was a late addition to the United States team for the 2019 FIBA Under-19 Women's Basketball World Cup in Thailand.

[51] She made her debut for the United States senior national team at the 2021 FIBA Women's AmeriCup in Puerto Rico.

Miller's two sisters have played college basketball: Adreana at La Salle and Ohio State, and LaNiya at Stony Brook and Wagner.