Did you give her the B complex? Could she have been walking the fence and getting stuck due to a vision or neuro problem or was she just being a silly lamb?
I don't have a lot to offer aside from wishes that she recover for you. It's really difficult when you have an animal who continuously tries to kill itself
Really sorry you lost her There isn't much you can do and you can't watch them all 24/7/365... This wasn't a "one off" and she had repeatedly gotten her head stuck in the fence. Hang in there Lady... There will be more lambs in your future that will need your love and attention.