The problem is that from the outside of the apartment no one knows the difference - they just see men entering and leaving the apartment - what would you think if your single neighbor all of a sudden had a man or men hanging around even for short periods of time.

I am not recommending she or anyone else do anything - I am giving her the reality of the situation - what she does is up to her. Just as those who have pointed out she should respect the laws and the culture of the country (which is the side I support and adhere to) - the laws also state you shouldn't exceed the speed limit, drive aggressively, etc. etc. - how many of us sometimes do one or all three?