Occasionally? Occasionally broody? We had an all out, everyone's invited broody party this spring/summer at our house. Goodness gracious, those RIR's. LOL
Good luck with your hen.
For me, sleeping in the nesting box is a sure sign of broodiness. You can give her some fertile eggs to incubate, or put her in a small cage to break her. If you can't get eggs for her, I'd break her. It's tough on them to brood for a long time with no results.
As far as RIR's not tending...