Is what this wife did—engaging in virtual sexual practices with strange men, masturbating during these acts, and watching pornographic films—considered zina (adultery/fornication)? What is her punishment? Will Allah accept her repentance and forgive her, and how can she overcome her guilt and satisfy her husband?

If the conditions of repentance are met, namely, desisting from the sin, regretting having committed it, and resolving not to return to it, then it is accepted, Allah willing. For Allah is Oft-Forgiving, Most Merciful; He accepts repentance and forgives all sins. There is no need to inform the husband of what happened. Rather, it is sufficient to strive in repentance and seeking forgiveness, and not to return to the sin. One may generally ask for his pardon and forgiveness for any shortcomings towards him, without mentioning the specific sin.