Consider that when a woman reports harassment and says "I don't want to cause trouble," it's coming from a lifetime of not having her experiences taken seriously and situations like this backfiring. <i>Boys will be boys, you shouldn't be dressing like that, maybe you shouldn't have lead him on..</i> and then the woman reporting the harassment gets labeled as the troublemaker instead of the real perpetrator.

Demonstrate that you are taking her experiences seriously and behavior like that exhibited by your new employee is not acceptable. Get him out of there.