My 7 year old son flys often into Dulles by himself and I always get a gate pass when picking him up. One time, my girlfriend was going with me and she bought a fully refundable ticket on Southwest to get through - no problems. On another occasion at Dulles, she was with me and just asked the Ticket agent if he would give her one. He kinda paused and said ok. I have had ticket agents specifically say that they will only allow one person to go through so YMMV.