She would reassign her benefits to the group. When she sees patients at the Neurologist's office, they are billed under her indiv NPI as the rendering provider, and the Neurologist's group info for the billing (Group NPI, EIN, etc). Payments for any patients seen at the Neurologist's will be paid to the group. When she sees patients for her private practice, they are billed under her info and still paid directly to her. It's done all the time. You just need a CMS 855R for Medicare.