How very, very sad. I agree that everything you are observing is connected. What concerns me beyond the lack of reaction to pain is the apparent regression to very primitive behavior.
It is indeed possible that she has reactive attachment disorder. When a child doesn’t have the nurturing and care they need when very little, the child doesn’t have a model for caring, for self-care and for socially normative behavior.
Unfortunately, it’s also possible that your daughter has another mental disorder. Autism, intellectual disability, childhood disintegrative disorder and childhood schizophrenia all include some of the symptoms you describe. That’s just to hazard a few guesses.
Without a clear diagnosis, therapy can’t be helpful. The therapist doesn’t know what should be treated. I urge you to take your daughter to a medical facility that specializes in childhood psychiatric problems. First, she should be thoroughly checked for any medical condition that may be contributing to her behavior. Then she needs to be screened by specialists in childhood psychiatry.
Having a chronically ill or mentally ill child is as stressful as it gets. I hope you and your husband are also getting help for yourselves. Ask your doctor for information about support groups for parents. Often other parents are the best source of information, support and practical help.
I wish you well.