What do I need to do to access my mother's medical records and speak to her doctor?

Speaking to your mother's doctor is done the same way as speaking to any other doctor; you make an appointment. If it is necessary to access your mother's medical records, her doctor has access to them and can access them for you. Of course, you will have to have a legitimate reason to have access to her records. I don't know what your reason is. If you are planning a malpractice suit against your mother's doctor, then the courts can subpoena the records.