Helena Christensen, 53, and Martha Hunt, 32, attend Gigi Hadid's 27th birthday bash in NYC

Bella Hadid cuts a sexy figure while celebrating sister Gigi's 27th birthday in NYC

Gigi Hadid looks ethereal in white lace as she celebrates her 27th birthday with an A-list bash

Blake Lively, Emily Ratajkowski, & More Stars Step Out for Gigi Hadid's 27th Birthday Party!