Funny behaviour

Of our two remaining hens one of them is behaving very oddly.  She is the second one to lay and stays in the nest box for about 2 hours.  This morning I went to see if she was OK as she seemed to have been in there longer than usual and she was having a nice time rearranging the staw in the nest box, picking up pieces and placeing them round her.  When she finally came out of the nest box she started picking up pieces of straw, almost examining them and then chucking them over her shoulder (left and right).  She carried on doing this when she came out of the hen house, picking up bits of bark lying on the ground and 'throwing them away'!  Is she having a spring clean?  I have never seen any of ours do this before.  It was really quite funny as she looked as though she was tidying up.

I don't think she is broody!  She is a hybrid and there are only the two girls and she does come out eventually.  Anyone else seen this 'cleaning' behaviour? (the house was cleaned out at the weekend by the way so it is all fresh and clean in there - or we thought so!).