Gigi Hadid 21st Birthday was a big party ..oops ..actually it was TWO big parties in LA and Vegas. Supermodel's star studded first party in LA was attended by BFF Kendall Jenner and Kylie Jenner, Naomi Campbell, Taylor Swift, Khloe Kardashian, Jaden Smith and many more. However her boyfriend Zayn Malik was missing for most of the night. Taylor Swift shared some cool selfies of the girl gang from the party on her Instagram and so did Khloe. In the second party in Vegas, Gigi was looking stunning in a plunging mini dress with bare back. Checkout her pics with the big Birthday Cake as well.