Shields' daughter Grier Henchy, 18, walked in the Tommy Hilfiger runway show during NYFW. Brooke Shields knows when she’s out of her element. In an exclusive interview with PEOPLE, the Blue Lagoon star opened up about what it was like watching her daughter, Grier Henchy, 18, make her runway debut during the Tommy Hilfiger fashion show at New York Fashion Week on Sept. 18.