Hm, well Pankaj, I can tell you this sounds very complicated. I am not Hindu myself, but my former boyfriend was from India so I know a lot about caste issues and astrolgy based stuff as it pertains to relationships.
Some people find these things very important in determining their partner, so much so that it doesn't matter how much they love you, they are afraid to go against the will of fate or God, for fear they will punished somehow in love. Being that she is not an atheist and you are means that you will have some very different views on these things, as will her family. I don't think she will change her mind, especially if her family is not supportive of the relationship.
I understand you love her, but you need to face reality. She is not going to defy her beliefs and her family. I don't think you should ask her to, either. You may consider these things 'silly', but obviously they are important to her and you should respect that. She shouldn'y have told you it wouldn't have been a problem, it's true, but maybe she just didn't ewant to face reality at that time.
My friend, there are a million girls out there, and one who will want to be with you no matter what. I suggest you let this girl go peacefully, and do not make a drama.
Live as if you were to die tomorrow. Learn as if you were to live forever. - Mohandas Gandhi