Let's get one thing straight during our discussion - she was not giving advice to the victims of the sexual assault / mobbing incident - she was giving advice about an up coming incident.
So upcoming incidents will be entirely different from the last one.
That makes no sense. The tactics won't change because they simply work. And you can't beat these tactics with these advises.
Well let's extend your example abit. Suppose you saw them approaching. And suppose you said nothing. My advice to you would be to call someone - the police - to come and assist you. Or to shout and raise an alarm. Which, of course, is precisely the advice the mayor gave.
You take your phone out: Its gone, they have it now. Happened in Köln.
Shout and raise an alarm: Not going to work because they surround you entirely and between them and the police/someone willing to help is a second row of perps to block off any help
But lets just say a few police officers are nearby. What now? They are facing 10 times as many perpetrators.
Happened in Köln. Couldn't do anything. Till the reinforcements are nearby your Girlfriends Vagina is bleeding, her clothes are ripped of etc.
Her friends, if female, are in the same situation.
If you were with her you are probably lying in your blood. Don't worry they won't kick your head too often. Just enough for you to never walk again.
Such is life I guess.
Could've all been prevented by simply keeping your distance. Literally no one would have ever had to die in history if someone else would've had that genius idea.
Caesar could've grown old. Man.