Technical, this won't help - it's in the Outlook store.
What you could do is let the message be delivered and then delete it... But I understand this is not exactly what you wanted to hear...
What was the name of the virus, again? (If you remember)
Does this happen often, or it only happened once?
Did she react immediately after she saw the virus warning (e.g. try the button 'Delete') or did she first call you -- I'm asking because it may be a timing thing -- if the warning is on the screen for a longer period of time, some extra actions are taken to prevent lockups...