[10] On September 23, 2018, she took part in The Educational Theatre Foundation's fourth annual Broadway Back to School event held at Feinstein's/54 Below.

[12] On January 12, 2019, Rapp performed at BroadwayCon's 2019 Star to Be event, singing "They Just Keep Moving the Line" from the NBC musical drama series Smash.

[15] On May 28, 2019, it was announced that Rapp would be taking over the role of Regina George in the Tony Award-nominated Broadway musical, Mean Girls, first for a limited run from June 7–26, then permanently starting September 10, 2019.

[16] On June 3, Rapp performed at The Green Room 42, singing songs from the show after an introduction by Tina Fey.

[19] On October 14, 2020, Rapp was cast as Leighton Murray, one of the four leads in Mindy Kaling's Max teen comedy series The Sex Lives of College Girls.

[24] In an October 2023 interview, Rapp said she has no desire to return to acting after Mean Girls as she wants to focus on her music career and because of the anxiety the environment gave her.

[30] On June 16, 2023, Rapp announced an international Snow Hard Feelings tour, supported by Alexander 23 and Towa Bird.

[31] On November 17, 2023, a deluxe version of Snow Angel was released, featuring four new songs, including a remix of "Tummy Hurts" with Coco Jones.

[40] In March 2024, Rapp and English musician Towa Bird made their public debut as a couple on the red carpet at the Vanity Fair Oscar party.