بسم الله الرحمن الرحيم
(Fatwa: 1198/301/TB=9/1434)
Try your best to get her back home to possible extent through the intervention of police. If you have made every possible effort, you may leave her. You must have been careless in his upbringing; otherwise she must not have gone to such extent. However, you should make every possible effort to get her back to Islam.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband
