Is the mother sinful for shunning her daughter who disobeyed her and got married against her will and displeased God?

It is not permissible to abandon one's wife for more than three days, unless there is a legitimate Sharia interest in doing so. The wife must apologize and reconcile. It is also advised to accept her apology and forgive her. If her marriage took place without the permission of her guardian (her father or whoever takes his place), then her marriage is invalid and must be annulled.