Is it a HIPPA violation to ask for a copy of a medical bill on my step daughter as I am the policy holder?

Is the stepchild legally an adult or a minor? If a minor does she live with you?

No it isn't a HIPAA if you are the policy holder.

It is not a HIPAA (not HIPPA) violation to ask for anything. But if the bill contains medical diagnosis and treatment info and you are not authorized by your step daughter to have that info, then it would be a violation for the medical provider to give it to you.

If your step daughter is a minor the bio parents is probably authorized to receive it. Your being the policy holder does not, automatically, give you the right to see the bill.