Lord have this woman realize that you have given us all free will. Even Christians have free will and sometimes they let the enemy come and use them to destroy our peace of mind and our faith in you. You are not the one allowing them to do evil things, they are the ones allowing themselves to become evil. That's why we should always put on the Armour of Jesus every morning to combat the enemy that is always ready to attack us.
Ephesians 6:10-18 tells us God's will for us is to:
"Be strong in the Lord and in the power of His might. Put on the whole armor of God, that you may be able to stand against the wiles of the devil. For we do not wrestle against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this age, against spiritual hosts of wickedness in the heavenly places. "Therefore take up the whole armor of God, that you may be able to withstand in the evil day, and having done all, to stand. Stand therefore, having girded your waist with truth, having put on the breastplate of righteousness, and having shod your feet with the preparation of the gospel of peace; above all, taking the shield of faith with which you will be able to quench all the fiery darts of the wicked one. "And take the helmet of salvation, and the sword of the Spirit, which is the word of God; praying always with all prayer and supplication in the Spirit, being watchful to this end with all perseverance and supplication for all the saints."
Heavenly Father help this woman become victorious and not turn against you, open her eyes so she can understand your love for her. Touch her husband's heart and open his eyes too, to the control his mother has over him. He should love his mother but to allow her to control him that way is not being a real man. Let him see he has a wife and child that need him and his responsibility now is them. Bind them back together with your love, forgiveness, understanding, fidelity, trust, and bring joy back into their lives. May they make you the cornerstone of their lives and marriage Lord for without you we are standing on sinking sand and will not stand. May they learn to love you above all things here on earth and in the universe. Give her the faith she needs to become stronger in you and know what a Great Loving Father You are. I ask and thank you in Jesus Precious Name so that you may be Glorified Heavenly Father, Amen!