Regarding finances

Hi, I am a married female and a native of Uttar Pradesh. I have an elder sister who is threatening my parents on a lot of issues. She claims that the fees for my education as well as the money for my marriage was paid partly by her . She also claims that her money was uses for paying for building the house that my parents live in. My parents say that she didn't pay any money for any of the issues. They paid for my marriage and my education by their money and they took a house loan for their house, the last EMI for which was paid last year. The loan tenure was for more than 15 years. My sister used to work in USA till 6 months back and her accounts in India were managed by my father. He has now handed over all the accounts to her and has not taken out any money from the accounts. The account statements proove the same. My sister transferred some money out of her own will in my father's account some 4 to 5 years back. She is asking for the details of that money. My parents say that whatever money was transferred was spent on my sister's marriage and her other needs. My sister is threatening to sue my parents and claims that the house (that is in my parents' name) should be given to her. Please advise me on what should be done in such a case.