We just completed the transition to a big girl bed for our 2 and a half year old. Shortly before our daughter turned two, we got a new crib (in anticipation of the birth of our new baby several months later). The crib's dropside could not be installed due to missing hardware, so for about a week she had to sleep in the toddler conversion of the crib. It was very disturbing to her, and meant a lot of sleepless nights like you've been experiencing. Once we got the hardware, we put it back to a crib (she just wasn't ready). In January of this year, we made a big deal of switching it to the toddler rail (she was 26 months). She learned to stay in bed until we got her (we only spanked twice). What made it different in the big switch to the twin bed (just occurred) is that it has always been set up in her room and she has napped on it every day (by choice). It was very hard (for me) to move her out of her special toddler bed to the twin. (I took lots of pictures!) In June we took a trip to Thomas the Tank Engine and a couple weeks after getting back I had a quilt made, special star sheets, and applique stickers to decorate the headboard and walls. We made a big deal about getting it ready. (In this process, we left her toddler bed as is.)
That first night, she slept in it very happily. 2nd night, on the floor with her special blanket and animals. 3rd night wanted the toddler bed. After that, she was happy to be in her Thomas train bed. About a week later, we worked together on her baby brother's bed, changing it back to the crib and setting up his sheets, mobile, etc. She was excited to do it. I think the big things that worked for us: 1) she stayed in her own room (small house; both kids in same room) 2) she could move over on her own timetable (within reason). We did not pressure her to make the switch, being gradual, it could be her own "decision" under our guidance. 3) she was already used to the twin from napping on it daily 4) I chose a theme that was "no-fail". She is so pleased to sleep with Thomas every night. Once her brother's crib was made up, we said, "No, that's his bed." We also did some rearranging so she has a little bookshelf by her bed with a lamp, her water bottle, and a place to put her pacifier. She feels really grown up.
We have only just in the last week started to put our 5-month-old in his crib in her room every night. My suggestion would be to take it slow, introduce only one new aspect every couple nights, and try to do it without pressure. She may be too young for all those changes right now. Is it possible to borrow another crib/bassinet to put in the nursery, and let your daughter have her crib in the new room with the other bed to get used to the whole idea?
Best of luck!