She is asking her husband to divorce her co-wife

Polygyny in Islam

Wife asking husband’s permission to fast when he has another wife

A man wants to take a second wife – would the second wife be sinning?

Conditions for plural marriage

The first wife’s approval is not a condition for marrying a second wife

How to start fair treatment between two wives

He has two wives and he is not dividing his time among them fairly

A wife giving up her right to maintenance; and is the first wife’s approval needed before one can marry a second wife?

There is no hadeeth which says that a wife’s permission is required before taking another wife