Answer
(Fatwa: 667/621=D/1429)
When the Hindu girl has embraced Islam and you are fully satisfied with her Islam that she had not become Muslim in greed of marrying you but she has accepted it sincerely and truly, then it is Islamically allowable to marry i.e. if you tie the knot with her, the nikah will be valid. But on the other hand, if your parents forbid you in view of any harm regarding your life, wealth and faith, then it is your duty to obey them. Yes, if there is no fear of any harm in religious or worldly matters at any cost, it is still better for you to obey your parents, in this case it mustahab (desirable) to stay obedient to them. However, if you marry her, the nikah will be valid.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband