Not real often, but sometimes, you'll end up with a 2 queen hive in late fall thru winter, and in the spring, the younger queen is usually the one that takes over the hive. At this point, you are not sure if the remaining queen is mated or not. You've not mentioned what the box configuration of the hive is. Bees need to be somewhat crowded, so if there is more than one box, remove some to reduce space. Bee sure to leave frames of honey and pollen with the box you leave in place. Not knowing for sure whether this queen is mated or not is the issue. You could add a frame or two of sealed brood with attached bees from another hive, if you have one that would not be too badly weakened by doing so. If not, just let this one sit the way it is after reducing space and see what happens. It could bee that this queen has very recently taken over posession of the hive as queen and so has not mated or laying yet. Another option, is to off this unknown queen and take the frames of bees and slip them into another hive as a boost. You could always make up a split later on when is more strength and nectar flow.
20+ years, raise my own queens, feed when needed. I treat, but have not perfected varroa management yet.