When it comes to greed , it comes out in full force when there is money/property involved . Family member will often turn into almost criminals to cut other family members out, seen it way to often . You cannot consider your other family members trust worthy. It is up to you to protect what your members wishes were, and if it is 50% then be prepared to do battle. Your sister pushing you away form your dad is a well used tactic when the end is near. Like other have clearly stated , lawyer up quickly. Get motions made to slow down the process or you will lose everything. She already thinks she has a end game in place. You job now is to disrupt it.