Is it haram for a Muslim girl and a Hindu boy to have a relationship?

I met a girl on social site and met her only once during her birthday. The main problem is that she’s a Muslim girl and I belong to a Hindu family. She refused by saying that her religion doesn’t allow to practice such things especially keeping it as a secret, so called as “**Haram**” and also concluded saying that her parents would disown her and reputation of the family will go down in the society. I never made any physical relationship with girl, not even a hug or sat very close together except just shaking hands just during her birthday. Never looked with bad intention and always lowered my eyes whenever I had a conversation to her. Is it haram for a Muslim girl and a Hindu boy to have a relationship? I have even asked [the question on Quora](https://www.quora.com/I-m-18-a-Hindu-boy-who-proposed-to-a-Muslim-girl-who-s-16-She-refused-by-saying-that-its-haram-to-have-a-secret-relation-Her-parents-would-disown-her-Her-reputation-will-go-down-in-the-society-Is-that-true-Why-Isnt) , hope if it helps someone in a similiar situation :)