Solitude and the feeling of delight about her engagement or wedding ring(I assume) made her feel braver. Perhaps because no one is there to tell her what to do, she feels in control. Is her marriage a step up for her, helping her to improve her position?

Perhaps her feeling of full control over the space made her feel stronger and more responsible. There may also be a lack of criticism involved. It is coupled with the feeling she has when she looks at the ring. Perhaps this has been given to her by someone who loves her and, therefore, makes her feel valued. This value, and maybe the expectation of seeing the person who gave her the ring, might give her a pride and responsibility over the space that motivates her to improve it. (In anticipation of the ring-giver arriving?) Sorry, that was a bit long-winded. Being alone and her feeling of love gave her the confidence and motivation to clean the room.