What is the ruling regarding a woman who vowed to sacrifice an animal for the sake of Allah the Almighty if her daughter is divorced due to her husband's ill-treatment of her?

If discord and ill-treatment persist between the spouses, and reconciliation is not possible, then divorce, in that case, oscillates between being obligatory and recommended. If the wife's mother or anyone else vows to slaughter an animal for the sake of Allah Almighty upon the occurrence of divorce, then her vow is valid and must be fulfilled if the divorce takes place.