Chelsy Davy Rocks Out at Matthew Morrison’s London Concert

 Samir Hussein/WireImage.com; Kevin Mazur/WireImage.com

Looks like Chelsy Davy's a gleek!

Prince Harry's on-again girlfriend, 25, took in Glee star Matthew Morrison's Monday night concert at London's Hammersmith Apollo arena. While her royal beau, 26, didn't attend the show, she had plenty of company. Among the 3,500 attendees at the show were Davy's pal Holly Branson and a gaggle of their girlfriends.

A source tells Us Weekly that Davy's favorite routine of the night was Morrison's cover of NSYNC's "This I Promise You," performed with the help of original NSYNCer JC Chasez.

"Chelsy definitely got into it when JC came on stage and sang! That was definitely a show highlight," says the insider.

Later, Davy partied with Morrison and his family and friends — including Princess Beatrice's boyfriend David Clark — at a private bash at Boujis nightclub. Out until 3 a.m., Harry's gal pal of four years was on her best behavior. "Chelsy was just hanging out, no flirting with guys," insists the source.

Named one of FHM magazine's "100 Sexiest Women" in 2008, Davy had better pack her summer full of nights out. Come September, the law-school grad begins work as a trainee at the elite law firm Allen & Overy.

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