tanya- really married to karan?

well as far as i was aware a man can only marry one woman so karan married nandini first and i dont think he ever divorced her but then he cant be married in the legal (or religious) sense to tanya. so does tanya not care that she isnt karan's legal wife?

so in that case shouldnt we feel sorry for nandini....it was after all tanya's fault to marry karan even though he was already married. she must've known that it isnt a legal marriage.