Hen won't leave the nesting box

[chickenscratch]

One of my chickens won't leave the nesting box. She's laying eggs but staying in the nesting box all day and night. I took her out and put her out with the other chickens and she eats a little, walks around and goes back in.
Any ideas on what wrong with her or what to look for.
Thanks

 

[CUDA]

She's trying to be broody.

 

[chickenranchwife]

She's a broody one. Set some eggs under her if you have some fertile ones available.