D.S.
Well, it might be kind of tricky since there will be another crib in the room with her, but when I transitioned my twins out of the crib, I made it sound like it was a good thing. I didn't let on it any way that it might be hard for them, I made it a cool thing. (Like getting to go to McDonalds the first time, cuz now your big enough). "How cool, it's time for a big kid bed, you're so lucky!" Then I had them "help" me take the crib apart and put together the new bed, let them pick out the sheets I was going to buy etc. Maybe talk about how jealous her sister will be...that kind of thing. Mine never had any issue with a change in sleep pattern, I did use those rails for safety and that made it a bit tricky to get out of the bed so I told them they had to call for me if they wanted to get out so that they didn't get hurt or knock the railings down. That was that. They never climbed out, not once. Good luck ~ D.