R.D.
That is a tough problem. I think the longer you wait the harder it will be. She is so used to sleeping with you I'm guessing there is probably going to be some crying, unfortunately.
I co-slept with both my children. I attempted to nap them early on in the crib so they would get used to it. Then around 6 mos I started putting them to bed in the crib for the first part of the night and brought them in the second half of the night. Then after a month or so I would get out of bed and nurse them and put them back into bed. Eventually they both started sleeping through the night on their own.
With my son, now 3, he went through a phase where he didn't want to go to bed. I'm guessing he was around 8 mos. We did a Ferber type routine where we'd let him cry 5 min, go in and sooth, 10 minutes, sooth, 20 min. sooth and then every 20 minutes after that. I think it took 2 hours the first night and maybe one the next and then he was fine after that. I was upset and crying as well but I knew he was ok as far as being fed, clean diaper, and not hurting since whenever I picked him up he'd quickly stop crying.
With my daughter there were a few nights where she'd cry for about 5 minutes and then would settle herself down.
I think it's ok to let them cry some because they do need to learn to settle themselves down. I think since your daughter is older I'm afraid it's going to be a little more difficult. I would suggest being really consistent when you decide to try to switch. Make sure you have a night time routine that you do with her at bedtime so she knows it's time to sleep. I'd probably start on a friday night since you'll probably have some sleepless nights.
Good luck-hope this helps!