Should Law and Religion mix?

I wanted to write this post for quite sometime ever since I read this news article. The article about how a high court declared a Muslim man's marriage to a Hindu girl null and void based on the religious rule that the girl should convert to Islam before the marriage. The fact that the man already has a wife is not lost on me and would have appreciated the ruling if it was based on this fact.I completely respect the religious rules and wouldn't have had any concerns if the Islamic body had declared this marriage null and void based on their religious practice. The freedom of religion would very well apply here. But the law stating the marriage void based on a religious rule does not seem right to me.

What happens to freedom of religion the girl in question has here? Is the law forcing her to convert because she wanted to marry the man she loves?Suppose, someone is not following the rules of his/her religion, would the court rule that the person should not practice or claim to be from the religion?

We have seen instances of caste discrimination all over the country. We are seeing honor killing in some parts of the country. Would the court rule all those marriages null and void just because a caste prohibits its people from marrying people from other castes? Isn't the basis of democracy is for a person to do what he wants to do as long as it is not against law and is exercising his free will? In this case, is the couple allowed to exercise their free will? Aren't we striving for a society where free will is not crushed in names of caste and religion?

Again, I am not against any religious rule as long as it does not discriminate or crush the freedom of a person, but is it the case here? Is this judgement in the right direction of religious freedom and free society?