SELENA
When Gomez turned 21 on July 22, she received a very special birthday message from a very special someone: longtime pal Taylor Swift, who wrote on Twitter, “Happy 21st birthday to my friend, and the closest thing I’ve ever had to a sister.” After covering the Red singer’s hit “I Knew You Were Trouble” at a January show, Gomez told PEOPLE, “I met [Swift] when she was 18. This is before [Swift’s 2008 album] Fearless came out, and it was absolutely incredible to see someone so successful and so humble. I think she has been a big part of me kind of staying the way I am too.”