My sister has Power of Attorney for my parents and refuses to speak to me about their care. What legal action can I take to access information about their assisted living care?

My parents are unaware that my sister is refusing to speak to me or offer information regarding their care- even when either of them is admitted to the hospital, falls, or receives emergency care. She also handles their money and family members suspect she is using their social security and benefits to pay her own expenses.
My husband and I have given my sister thousands of dollars for her rent, car payment, bills, etc., but she cut off communication when we let her know we could not keep covering for her. She lives in the same state and city as my parents (we helped move her, paid her security deposits, rent, car payments, gave her money, bought furniture and items for her house, etc.). We have also been sending checks to my parents- many for a few hundred dollars- and she is authorized to cash them and 'dole out' the money to our parents as she sees fit. Family members are suspicious that she keeps part or most of the money, so we have begun sending checks to my maternal aunt. HELP!