She looks to me like she is ready to start laying at any time now. Most of my birds started laying between 20 and 24 weeks. I had a couple of pullets that started laying at 17 weeks.
Is she a Gold Sex-Link? Her feathers are just like one of our pullets', Ruby, who just started laying this past week. She was about nineteen weeks. Your girl will probably be laying any time now! I know how horrible it was to wait it seemed like FOREVER!