Since there is still time before the twins come, maybe you can tell DD that she can sleep with you every night for X number of days, make one of those construction paper loop things to tear off and count the days, and once the days are done she gets a reward when she stays in her bed. She has a tangible way to keep track of time, and knows she's being kicked out of bed because the twins are so close, not because they'll be here eventually.
When I was little we had fold-up foam "futons" that fit in a closet but folded out to about the size of a single bed. We each had one color that was ours, and if we got permission, we could sleep on one of those wherever we wanted, even in a tent in the backyard some nights or in the bathtub (as a PP mentioned). Here's an example, though I'm sure you can find similar much cheaper: http://www.foamorder.com/trifolds.html . Really though, I spent many nights with my older sister, I was always one that needed company to sleep.
When I was little we had fold-up foam "futons" that fit in a closet but folded out to about the size of a single bed. We each had one color that was ours, and if we got permission, we could sleep on one of those wherever we wanted, even in a tent in the backyard some nights or in the bathtub (as a PP mentioned). Here's an example, though I'm sure you can find similar much cheaper: http://www.foamorder.com/trifolds.html . Really though, I spent many nights with my older sister, I was always one that needed company to sleep.
