score:3
Sorry to hear this.
She'll need to report the stolen visa to the US consulate via email. The information required is listed on that page. The contact info for the Vienna Embassy can be found online.
I would make the report immediately, advising them of the urgency of the situation and requesting a replacement visa. They will take the report and advise on the local procedures, arranging for her to come to the consular section for a new visa. Unfortunately, it may not be possible to get the replacement processed in time, as there are just two working days left, so I'd start making preliminary plans in case it is necessary to delay her trip.