What is the ruling on a wife performing Istikhara for divorce without her husband's knowledge, even while she attempts to treat him kindly?

A woman is allowed to perform Istikhara regarding her request for divorce if the request itself is permissible. It is not permissible to request a divorce without a legitimate religious reason, such as harm to the woman due to the husband's bad character, his inability to provide for her maintenance, or his immorality. If a legitimate reason for requesting a divorce exists, then Istikhara is permissible; otherwise, it is not.