The 17-year-old actress, an unknown prior to landing the role of Maria in Steven Spielberg's new adaptation of the movie musical, shared a shot of herself and Ansel on her Instagram page after the show.
Alongside the snap, Rachel, who played Princess Fiona in the school production, wrote: "Met this FAN at the stagedoor! he was pretty cool! not sure if y'all have heard of him? pretty sure his name's tony."
"Baby Driver" star Ansel, 25, will be playing Rachel's love interest Tony in the highly-anticipated film.
New Jersey teen Rachel was one of 30,000 people who auditioned for the role of Maria, before landing the part which was played by Natalie Wood in the 1961 original.
Rachel joins a star-studded cast including Broadway veterans Ariana DeBose as Anita and David Alvarez as Bernardo, while Josh Andres Rivera has been cast as Chino.
After her casting was announced, Rachel said in a statement: "I am so thrilled to be playing the iconic role of Maria alongside this amazing cast. 'West Side Story' was the first musical I encountered with a Latina lead character. As a Colombian-American, I am humbled by the opportunity to play a role that means so much to the Hispanic community."
The original 1961 movie was adapted for the screen from the 1957 Broadway musical, written by Arthur Laurents with music by Leonard Bernstein, lyrics by Stephen Sondheim and concept, direction and choreography by Jerome Robbins.
Filming on the new adaptation is scheduled to start in the summer.