Is a wife who knows nothing about her husband, who has been absent for six years, considered divorced, and is it permissible for her to divorce herself if she is unable to appear before a judge?

The original state is the continuity of marriage, and a married woman is not permitted to marry another. A mere ruling of separation by a secular court is not considered a valid termination of the marriage according to Islamic law. If a ruling for separation is issued for you by an Islamic legal authority, then you may document this with the court to ensure legal protection when you marry after the iddah (waiting period) expires. We advise you to be patient, fear Allah, and stay away from whatever incites discord and desires.