Taylor Swift Celebrates With One Direction’s Niall Horan and Louis Tomlinson After Billboard Music Awards; Ex-boyfriend Harry Styles Absent?

Taylor Swift celebrated her eight Billboard Music Award wins with a star-studded afterparty attended by her brother Austin, boyfriend Calvin Harris, BFF Ed Sheeran, and One Direction’s Niall Horan and Louis Tomlinson, among others. But ex-boyfriend and One Direction band member Harry Styles was noticeably absent from the festivities.

The 25-year-old music superstar, along with Sheeran, threw an afterparty for the event’s attendees Sunday at the Nobu Villa at Nobu Hotel Caesars Palace in Las Vegas. The singer/songwriter brought her brother to Las Vegas after his college commencement ceremony in Indiana. Also in attendance was Adrian Grenier, David Guetta, Fifth Harmony, Jennifer Lopez and Pentatonix, among others, reports E! News today.

One Direction's Niall Horan and Louis Tomlinson also posed for a picture with Swift that night. Styles, who dated Swift for 4 months in 2013, was the only member of One Direction who did not attend, according to the Washington Post. The 21-year-old singer flew back to Los Angeles in order to avoid seeing Swift with new boyfriend Harris.

Another person missing from the "Bad Blood" singer’s afterparty was Rita Ora, ex-girlfriend of Harris. The “I Will Never Let You Down” singer reportedly stayed backstage at the BMAs to avoid the couple, reported the Mirror. Ora and Harris went through a bitter breakup last year -- but regardless of where she stands with Harris, the British pop star has spoken about how she respects Swift and loves her music. "I think she's one of the most incredible songwriters of our generation. I'm not even just saying it,” she adds. “I absolutely adore her music and love what she stands for."