When nothing seems to help, and there's nothing physically wrong, it's time to look into emotional or other psychological issues. Your child may not like having the wet bed, or needing to wear diapers, but she evidently is receiving more attention because of her problem. I suggest you take her and her sister with you to see a family counselor, and see if you can get to the root of her problem. I also believe that when one twin has a problem, the other could be having one, too, but may be suppressing it. Or, one twin may be more popular than the other. Also, whatever issues are discovered could also become a problem for their brother sometime in the future.