Disagreeing family member

My father built a house and registered it under his mother's name and his. My father has an elder brother, who's settled abroad and a younger brother and sister, both of whom reside in our house. Initially everybody hated the house and the father had to clear a lot of debts from building the house. He worked very hard before and after marriage and sent most of his salary to pay off the debt. Instead of paying off the loan his parents used most of his money for their own needs. After the value of the land increased they didn't let my father sell the house, as they demanded equal shares for everyone. My mother had to go through verbal and mental abuse from my grand parents and aunt, who divorced and abused her husband and never took care of her child. Due to which we (my father, mother, brother, 10 and i, 8 then) moved to a rented place for almost 9 years. After 9 years my grandfather passed away and we came back to the house and my grandmother still refused to sell the place or write a will. after 3 years my grandmother passed away without writing a will. The younger brother and eldest brother want to sell the house and have no disagreements but the younger sister refuses to sign as she wants us to pay her a part of our share and 5 lakhs. When we moved to a rented establishment the younger sister paid off the loan without telling my father, he agreed to pay her back the principal amount when we sold the house and they agreed. She's asking us to pay her back with interest now. She never took care of my grandparents and her daughter, she lived off of everybody else's money. Now she doesn't pay for the water or electricity. She's been living here for years and she verbally abuses us and lies to distant relatives and neighbours about us. If we were to legally split the property into 8 shares, 4/8 belongs to my father and the other half from the grandmother's share gets split into 4 among the 4 children, but the aunt wants our share from the other half, i. e., (1/4) including the 5 lakhs. (There was no prior agreement to pay with interest, we would have paid it off ourselves) We've been suffering for a very long time. Is there anything we can do to legally move on with this and sell our house? She refuses to sign the documents necessary. She doesn't work anywhere she's lazy and dishonest and doesn't help out at home also. She sits at home eating and wasting her time on the phone calling random people.