Is it permissible in Islam for a wife who has been psychologically harmed by her husband to seek a divorce, when he refuses to divorce her in order to prevent her from marrying someone else?

Civil divorce issued by Western courts is void if it is un-Islamic. The husband should have divorced you when you disliked him. If he did not, then seek khul' from him by returning the mahr (dowry) or whatever you both agree upon. If he refuses, go to an Islamic center. If they rule that you are entitled to a divorce, then file a case in the civil courts. Then return to the center to evaluate the judgment. If they permit it, the Islamic divorce takes place.