(I understand losing your spouse to another, as I'm in this same situation myself, but not knocking my husband to my children)
Lord, please bless Stacy with another person who will walk through this fire with her, that is not her child. Let her find comfort in You, Lord, knowing that regardless of how this looks, her marriage does matter to you. Father, above all, I pray for changes in Stacy AND her husband that would bring glory to Your name and restoration for their marriage.
Let Stacy's angry words fall to the ground if she speaks them to her son Zach. Give her son the courage to speak Your words to his mother in defense of his family. Open Stacy's eyes to see that a child should never be forced to choose which parent to love, and that this separation hurts him as well. It's all to Your glory Lord, as you bring healing and restoration to this family. Praise You Lord for mending broken hearts, and healing a broken marriage, in Jesus name. Amen