What are the daughter's rights in her mother's property

I am Hindu, My Mother purchased property in 1973, After her death in 31st Dec 2003, My father, My Elder Sister, My Elder Brother and Me are the legal heirs, as per certificate. In 2004 in presence of my father, sister made Affidavit in front joint director of land records saying no need of her name to be entered in property, and same has been removed. IN 2013 my father died and Only My elder brother and me left in the property name. IN 2015 my sister signed registered release deed and released 1/3rd share (Sub registrar office) from the property. After that as we (both brothers) are developing property now she filed a case in court for 1/3rd share. She is asking from null and void of registered release deed of worth 1.5cr, Under Karnataka law fee we are asking court to take fee from her. Meanwhile court granted injection under 39 rule 1&2 cpc. Please help me.