Stop Social Security Authorized Representative Payee misuse of the elderly benefits and personal property.

I've have contacted SSA about this issue several times. SSA has not enforced the rules of law concerning the misuse of benefits and personal property of my elderly mother. My sister is my mother's authorized representative payee. She has been misusing my mother's benefits and personal property for years. SSA has allowed or failed to investigate. I don't know where to go from here. Please investigate as to why SSA refusing to enforce the rules that SSA has set for the protection of benefit misuse of SS recipients.