Provider Not Supplying Medical Records

My mom has a combination of Medicare and Medicaid, where Medicare is her primary insurance (pays 80%) and Medicaid is her secondary insurance (pays 20%). She was in a subacute rehab facility for about 3 months. The initial adverse determination denial notice from medicaid says that “To verify that the benefits described above are within the scope of the plan’s coverage, the service are/were medically necessary and are/were a covered service, we need the following information: Pending Receipt of Medical Records. We have also asked the health care provider who performed the service listed above to provide the information. We need this information within 45 days of the time you receive this request. […] Failure to submit the information within the required time frames may result in the claim being denied”.

She’s been receiving notices for the past few months saying that they are waiting for the provider to give them the appropriate medical records, that the services she received were “not medically necessary”, and that the “member [is] not liable”. What makes this more complicated is that I worry the facility is not providing her medical records on purpose, because we are suing them for mistreatment of my mom during her stay. Is it our fault if they do not provide the necessary medical records? Is there a way that I can provide the medical records myself? I don’t even know what medical records they need. Should I contact a lawyer for advice? It is very difficult to get in touch with anyone at the facility, which has been an issue since she was a patient there. We have not done anything yet because we have been waiting on the facility and because the paperwork says “member not liable”.