are very smart with long memories.
It may have really hurt when she was constipated and now she remembers that and may be saying it hurts as she feels stool pushing at the rectum. If her poops are not hard or huge and she can pass them uneventfully, i would put vaseline on her anus a couple times a day. It is simple and tell her it is to keep it from hurting. If continues, see your doctor.