Marked queen gone, unmarked queen laying — a supersedure I never saw. Is she properly mated this late?

Kent, third year, four hives. Did what I thought would be a quick last brood check yesterday on hive two and my blue-marked 2025 queen is nowhere. Instead there's an unmarked, quite large, pale queen walking around like she owns the place, eggs on three frames and capped worker brood in a solid pattern. I never saw a queen cell all summer — though I'll admit August inspections were brief because of the wasps. So they superseded her at some point in the last month or so without me noticing. My worry is timing. Drones have been getting kicked out here since early September. If she only got mated in, say, the second week of September, was there enough around for her to mate properly? And how would I tell a badly mated queen from a good one at this point? Do I leave her, or should I have a spare mated queen up my sleeve?