A got to the the circle first and GE was not overlapped so GE was not entitled to bouy room. That situation never changed even after A tacked the bouy room issue was settled when A got to the circle first and GE had no overlap, GE would have had no rights for room no matter what.
It appears to me that Artemis (A) tacked between 2-3 boatlengths from the mark, so I conclude that she entered the zone on port tack clear ahead of Groupe Edmond (GE). While A remains on port tack, she is not obligated to give GE mark-room. Instead, GE is obligated to give A mark-room under rule 18.2(b). When A passes head-to-wind, the obligations change. Rule 18.2(b) no longer applies (see rule 18.2(c)). That happens two seconds into the encounter, so rule 18 never really comes into play.
