With the greatest of respect underahat, the way harassmentallegations actually work is that everyone associated with the matter will have their careers truncated. That means you, the girl, the alleged harrasser, and anyone else silly enough to put their oar inirrespective of the rights or wrongs of the allegation.
I know its not fair, but large organisations simply do not want to have to deal with such matters and have a tendency to shoot the messengers as well as the guilty and innocent parties.
You will be labelled as a "busy body" and woe betide you if the harasser either gets away with it or the girl succumbs to pressure and does not proceed with a complaint. Your career will be terminated for "lack of judgement".
The most likely outcome if the woman is a civilian contractor is that she will be offered a modest sum of money to go away. If she refuses that, then she will be made to prove her case, with the odds stacked against her because of the authorities fondness for "natural justice" and "procedural fairness", that is unless the blighter concerned has had it coming to him for a long time and the authorities knives have already been sharpened.
Translation: This is a "no win" situation, especially for you.