Mother-in-law has demenia and in rest home. She has financial advisor but never signed power of attorney to authorize the money to be spent.

My husband needs to get money she set aside annuities set aside to buy her nursing home bills! She has Altheimers and "legally" cannot sign the pertinent form to authorize this money for the financial advisor. He suggests that we can have her sign and "not tell him about Altzheimers" since it isn't for fraud but ONLY to do her wishes for long term care. However my husband is worried since it isn't legal! He will check into guardianship but in the meantime his Mom's bills need paid the her money is right there. Please help!