Problem in marrying a bohra girl

I am hindu. My girl friend is Bohra from Udaipur, India. We have a relation of 4 years. We asked her parents for our marriage. Following is their response "As per quoran- A bohra man can marry hindu girl but a hindu man can never marry a bohra girl". They are forcing the girl to marry a bohra boy. How can i marry her? Also if whatever they are saying is correct then this rule seems to be wrong.