She accepted and asked for 15 days to move out. After 15 days she said she wont be moving out since my father has a share in the house . they would be living in my house in one room belonging to my father .
Actually your father has just helped you financially and is not a share holder in the property, hence this property belongs absolutely to you alone, therefore you can ask both of them to vacate the house and handover vacant possession or to pay rent till the period they are evicted by a court order.
My father also started blackmailing me that he would put reverse mortagage case against me for 12 Lakhs if i dont allow my sister to stay.
Your father cannot create or enter into a mortgage with you without your consent at this stage. You can refuse to sign the mortgage papers and even refuse to share the property even though he helped you financially towards the purchase of this property. You can inform him that you would repay the loan amount gradually otherwise let him approach court for recovery by due process of law.
My sister successfully started a fight and instigated my father to not pay a single penny and house hold items .
What can i do in such a scenario?
You should not leave your house with them and move out for any reason.
It is your property and you are the only person who has full rights in it.
You issue legal notice to vacate the property and file an eviction suit to evict them through court order.
Do not entertain their request to stay back and trouble you or keep interfering in your personal and family affairs.