Muslim - Hindu Marriage Survival?

[soundarya]

@tammy8604

I have a friend from US whos mom is a hindu and father is a muslim. Shes almost my age and shes both hindu and muslim. Obviously her father isn’t really practicing muslim, he drinks and everything but shes just muslim by name. She doesn’t know anything about Islam really, but calls her self half muslim. She was never confused about her identity, she was happy to be part of both.
My aunt (chachi) is from India and she told me these kind of hindu-muslim marriages are very common over there, not just limited to people from bollywood. Apparently many of our distant relatives are married off to hindus.

How can anyone even be half-Muslim? It’s not an ethnicity, it’s a religion.