Hide their pain, but usually its noticeable as in fluffed up feathers and not joining in with the flock. If she's acting normal, then I wouldn't worry too much. She probably can't roost with the deformity.
Sorry to hear that. It could be she was born with deformities and there's not much you can do. But, if in pain, you might want to consider euthanizing. :hugs
Is she having any other issues? If it is a pelvic deformity as mentioned above, she might have laying issues or she might not ever lay an egg. If she's not in pain and doesn't have any deteriorating issues, I'd let her be to enjoy life as is.