Sleeping in the nesting box, anyone?

So one of my RIR hens spent about 3 hours in the nest box 'laying' today. She definitely DID lay an egg while she was in there as I got 6 eggs from 6 hens in total today, and collect 3 times a day, so I'm 100% positive none were from yesterday.

Eventually I lifted her out of the nest box and guided her out into the run with the others, where she did the loudest egg song I've EVER heard, and it went on for ages.

Tonight when I went to lock them in their coop for the night, there she was. Back in the nest box.

I picked her up and put her on the roost with the others where she would normally sleep.

She did the egg song again - super loud, for a long, long time. She upset all the others who were boking along with her too.

I watched from the gate as she walked down off the roost and back into the nesting box to sleep. Everyone went quiet and that was the end of it.

I don't want to upset her any further tonight, but what should I do tomorrow? She (along with the others) ALWAYS sleep on the roost so I don't quite know why she's changed her mind about this. I don't want it to become a habit.

Should I just boot her out of the nest box tomorrow morning? She still needs access to it to lay.

She's not quite like the broody hens I've seen. Not flattened out, not growling, but she did peck a bit and protested loudly!

She was sitting on 4 plastic and 4 real eggs (3 of which were not hers), and I've removed all of them.

I didn't think RIR's went broody?

What gives? What should I do? They are nearly 9 months old.

- Krista