1. Legally you are not any way liable to her, if you did not have a physical relationship with her, have the courage to call off the marriage and offer to compensate for their loss if any. Hope that you have not accepted any money from her family. As no one can force you to marry anyone.
2.If in case you were in a living -in relationship or had a physical relationship with her, you should handle it wisely, as she can file a complaint under 376 and 506 . Try to end the issue amicably and call off the marriage .There will be certainly problems due to the girl's psychological immaturity.The demands cannot be such a way that you should cut your ties with your family, this will not allow you to breath when she threatens you for every small issues or for her demands .
4. In case they do not come or agree for canceling the marriage, send them a legal notice , by calling off marriage . State the specific reasons as you have mentioned in your question . This will pressurize them to come forward for a settlement and also help you as a defense.