The old beekeepers saying:He thinks I should try to find the queen in the swarm hive, kill her and reunite the hive. He said or try to reunite the hive and let the queens fight it out.
A swarm in May is worth a load of hay;
a swarm in June is worth a silver spoon;
but a swarm in July is not worth a fly.
Your mentor is right. But I would snuff out the queen in the swarm and paper combine the bees with the young queen in the parent hive. And give them the deep frames of honey.