Who knew Ashlee was such a fan? Ashlee Simpson-Wentz leaps to her feet Monday night while watching tennis star Roger Federer triumph at the U.S. Open tournament in New York.

Also in the singer’s cheering section: Cameron Diaz and husband Pete Wentz.

In related news: Ashlee dished on her sister Jessica’s love life this weekend, telling US of Jess’ new romance with her beau Eric Johnson, “She is happy, so we are all really happy. Her happiness is the most important thing to me.”

According to Ashlee, Jessica won’t be rushing into marriage or motherhood – for now she’s enjoying just being an auntie to 1-1/2-year-old Bronx Mowgli.

“She does love being an aunt though. She is a great aunt,” Ashlee says. “Yesterday Bronx was over at her house calling her ‘Jess’ [and then saying] ‘ica’ a few minutes later. It was really cute.”

Source: pynkcelebrity.com