Interest on house property

Sir, A Lady (X) Purchased a Residential House in her name in the year 2015. She has taken Housing Loan on the same. Her father (Y) is the First Loan holder in the Banks Loan account, whereas his name is not written in the Registered Property Deed. She is Co - Obligant in the Bank Loan documents. She is using the same as self occupied House Property and want to avail benefit of Interest on Housing loan and Repayment of Housing Loan since the Loan was taken by her to Purchase the property. Now, She want to take benefit of the Interest on House Loan and Repayment of Loan as Self Occupied Property. Queries: 1. Whether her Father can take 50% benefit of Interest on House Property and Loan Re payment , whereas he is not owner of the Property? 2. Whether its necessary that property should be in the name of the person who is taking benefit of Interest on House Property and House Loan Repayment/ Kindly advise and oblige.