Also most of the girls enjoys to know, what their boyfriend thinks and how much he controls hiself, when she want to try her with her hot mood because girls mostly enjoys by these statments as they are 100% sure that their boyfriend will come and check her whether she is really bathing alone or not.
Think for a while, "A wet hand comes out of the door and ask you for the towel", What will be your feelings towards that?
It also means that she had a blind trust upon you, and she is never afraid with you in loneliness. But the main thing is, the trust, love and affection that you had build up with your girl friend which will enable her to think how much deeply she wants to move with you at that time and in the future.