The pain you are carrying is real and heavy. Betrayal from a family member, especially in a time of grief, cuts deeper than almost any other wound. Your desire for truth, justice, and honesty is not born from vengeance; it flows from a heart that longs for things to be set right, for your mother's dignity to be honored, and for the Lord to be glorified. That longing itself is evidence that the true wisdom from above is already at work in you.
Whenever I think about wisdom, I remember that it is meant to lead us into justice, judgment, and equity. Yet there is a counterfeita wisdom that is earthly, driven by selfish ambition and envy. It creates exactly the kind of strife and deception you are now facing. That kind of wisdom does not come from God. It brings nothing but confusion and grief. You are seeing its bitter fruit up close. In much earthly wisdom there is much sorrow, and heaping up knowledge without the fear of the Lord only increases vexation of spirit. Your sister's actions may have seemed shrewd, but the path she chose is foolishness in God's sight.
So I pray with you that the Lord will reign sovereignly over every detail of this estate. The Scripture declares that all the treasures of wisdom and knowledge are hidden in Christ. He is the very wisdom of God made real to us. Because of that, you can ask Him for the wisdom you need, and He gives it freely, without finding fault. That wisdom is pure, peaceable, gently, and full of mercy. It will guard your heart against bitterness even as you seek what is fair. It will give you and your husband discretion when you face difficult decisions about the property and possessions. It will sharpen your discernment so you can see the situation as it truly is, not filtered through despair or anger.
I am also praying for your sister. The fear of the Lord is the beginning of true wisdom, and a heart that fears Him will hate pride, arrogance, and the perverse mouth that covers wrongdoing. Only God can bring her to the point where she sees her actions honestly and becomes willing to make a full accounting. Ask Jesus to move her heart with such conviction that there can be complete transparency about every transaction. That would honor your mother's memory more than any legal victory alone.
But even as you pursue what is right, remember that the highest wisdom is not merely to win a settlement but to walk in fellowship with Christ through this valley. He is your defense, far more than money or human strategy could ever be. He gives life to those who have Him. Your grief and the long burden of stressthese He understands. The sleepless nights, the medication, the feeling of being blamed unfairly: He is close to the brokenhearted. Lean on Him for rest that no sleeping pill can provide. His wisdom will lead you in paths of righteousness, not into the vexation of spirit that earthly wisdom invariably brings.
Keep asking for courage and grace, for those are exactly what He promises to supply. You are not alone in this. The outcome may take time, and it may not look exactly as you hope, but God will be glorified through your dependence on Him. In the end, the wisdom from above yields a harvest of righteousness and peace. May that peace guard your heart and mind in Christ Jesus until every hidden thing is brought into the light and justice is done.