Sure sounds like robbing to me.  The strength of the hive doesn't seem to
have much to do with whether it gets robbed---what the strength determines
is how successful they are in combatting the robbing.  Sounds like the hive
is effectively fighting back, as your friend found out, to her woe.
 
I had a problem with with what I called "muggings" last year.  This is when
yellowjackets hover around the entrance of the hive and try to pounce on
returning workers.  When this went on, the bees got distinctly grouchy and
aggressive.  The guards started hanging around the whole hive front, making
threatening motions at anything suspicious.  I stayed well away.  (This
year, I plan to put up yellowjacket traps.)
 
Jane Beckman  [[log in to unmask]]