Is it permissible, Islamically, to marry a married woman who is having problems with her husband and wishes to leave him and marry me, knowing that my wife may not approve of this marriage?

You must cut off all contact with that woman, and do not promise to marry her, for that would corrupt her relationship with her husband; based on the Prophet’s (peace and blessings be upon him) saying: "He is not of us who incites a woman against her husband." Scholars have differed on the validity of the marriage of one who incites a woman against her husband to the woman he incited. The Malikis and some Hanbalis are of the opinion that such a marriage is invalid as a punishment for him.