Doubt about the overlap
The situation
As the leaders reach the zone at the top mark, it's genuinely unclear whether Sofia (outside) and the boat inside her were overlapped at the moment the first of them reached the zone.
The question
Who gets the benefit of the doubt?
The ruling
If there's reasonable doubt that an overlap was established (or broken) in time, the rules presume it was not (rule 18.2). So if it's unclear whether the inside boat had her overlap when the first boat reached the zone, she's presumed not to have it — she gets no mark-room and must keep clear and round behind. The lesson for the inside boat: establish the overlap clearly and early, well before the zone, or you won't get the room.
Doubt about a last-second overlap at the zone? It's presumed there wasn't one — get your overlap clearly and early (rule 18.2).
Opens the situation on the boat-length grid — scrub it and see exactly how the boats meet. Free, no account needed.
Rules cited
See the underlying rule: Rule 18 — Mark-Room at a Windward Mark.