Our daughter made the transition when she was about 18 months old. I put her in the crib one day for her nap, and the next thing I knew she was knocking on the door! My husband, his brother and his sister all suffered broken arms climbing out of cribs so it was no real option for us. But anyway, back to the question.

Children handle change differently. I can still remember when my parents transitioned me from the crib. My brother was born and they made a big deal about how I was a big girl now, so I got to have the big girl room! They took me out to pick out my own sheets, and showed me my brother who was the baby and needed the crib because babies use cribs and I was a big girl now.

Our daughter we expected her to climb out multiple times and had set up camp at her door waiting on it when we put her down. To this day she won't get out of the bed until we open the door. Don't ask me how we got that lucky the next one will be a terror I promise!

If she had gotten up though we would have calmly put her back however many times it took. Not mean, no talking, just pick them up and put them back. If you talk, or even tell them you love them, hugs, kisses, etc. you just feed their energy. The best thing is to let them know with actions that they will be going back until they get the point. (Nanny 911 is a great show to watch with this one, they show some great examples there. Make sure the kids are asleep though you don't want them to see the kids on TV acting like they do!)

Something the sister can use until you are ready for the transition would be the pack n play, playpen. If you get it from WalMart and keep the receipt you will have 3 months to return it and get all your money back.

Make the change something for your daughter to look forward to. With my daughter we did very similar to what my parents had done. Earlier than planned but hey! One of our friends got her a fuzzy cat that is big enough for her to lay on, so we used it as the "new" thing. She "helped" us convert the crib into a "big girl bed" and when it came time for bed we did the same routine as always, just put her in the toddler bed instead of the crib.

If your daughter can talk, you also may want to try asking her why she doesn't like the new bed. It could be that she feels threatened she will lose everything to the new sister, or sometimes it is something as simple as they don't like the color (I went through that too, yes I was a pain as a child :) ), or something else about it that you don't even realize, but would be easy to fix.

Hopefully your nights get easier! Best of luck!