What breed is she? What are you feeding her? Approximately how much light is she getting a day? Is she free-ranging, meaning she has the chance to hide eggs from you?
I feel for you. Two of my girls waited until they were 38 weeks before they gave me their first eggs.
If she's not hiding the nest, maybe it's her. One of our EEs was 41 weeks old before she started laying. All of our others started between 18-22 weeks.