If you want her to sleep in her own bed/crib and not with you, then you will need to require her to do so. To say that "she won't" really just means that you don't require her to. She is 6 months old... it's not like she is getting out of her crib on her own.
Assuming that she was sleeping in her crib nicely before the sofa episodes, then you just need to go back to what you were doing before. Don't ignore her while she cries (and she will cry some), but don't give in, either. Comfort her (without picking her up) and then leave for a few moments/minutes... if she cries again, go in and comfort again (without picking up). Continue this process (going in to comfort without picking her up and then leaving again) until she goes to sleep - on her own without being removed from her crib. Yes, it will take a while. But she will fall asleep. And after a night or two, possible 3, she should be going to sleep on her own in her crib with no problems.
The reason she cries at bedtime is that she knows that it works to get her out of the crib. You've been teaching her that. Now teach her that she sleeps in her crib at bedtime, not just naptime.
Good luck.