First thing, YOU need to stay out of it. The employer is not obligated to talk to you about your wife's employment and you may end up making things worse for her. This is her battle to fight; of course you should be supportive but you need to let her deal with it herself. By getting directly involved (without her knowing) you put her on the spot with her employer.

Before I take this any further, what relationship is the alleged harasser to your wife in the workplace? Is he a co-worker, manager, supervisor?