My Dad had dementia and gave my cousin POA. She took 57,000 from his account. Can she do this?

He gave my cousin POA she then took 57000 from his account and placed it in another account of which she is their poa without tellIng anyone but that person. After my father passed he will named my sister poa and that everthing he had was to be spilt between his 3 children evenly there after this lady removed 57000 she left 13000 in the account can she do this