Notice of auction/warrant of levy should be sent to delinquent owner

Dear PAO,

My aunt bought a parcel of land, and a corresponding transfer certificate of title was issued to her. For unexplained reasons, the tax declaration of the land in the name of the previous owner was never canceled. She failed to pay the real property tax, and she divulged to me that the notice of auction/warrant was sent to the previous owner as reflected in the tax declaration. The treasurer's office allegedly informed her that they have no obligation to know the real owner of the property. Is there a violation of the right of my aunt under the circumstances?