1. Your father has committed more than one offence. By having a live in with another lady before divorcing his wife he has made himself liable to be prosecuted and punished for adultery. Your mother can prosecute him for adultery by filing the case in the court.
2. So far as the property registered in your name, which has no been usurped by this lady, is concerned, you can file a lawsuit for eviction to evict her from the property.
3. The fact that you are not a citizen of India does not stop you from filing the case.
4. Police has no role to play in this case.
5. The only legal recourse available to you is to move to court and file for her eviction. Her political links, if any, will not work in the court.
6. Engage a seasoned lawyer and get going.