Yeah I second trying just days for a bit. Oskar decided one day he wanted to sleep in his room in his big bed but when push came to shove that night... whole different ball game and we just had to let him go and sleep in his cot. He obviously felt secure. Then one day after we moved his room around a bit, bought new sheets and doona cover and made it all so very cool.. he just decided to move from his cot, which was in our room next to my side of the bed, into his own room and big boy bed all in one go and never came back lol. You could also try the mattress on the floor in case she's just feeling unsure about it with no sides? I know she slept there in the day, but for some reason night time is just a different game with them.