I ended up with an extra queen, so I put her in a 5 frame nuc with a frame of capped brood with nurse bees, and two frames with stores. I released her after 5 days and there was no trouble with them accepting her, except there weren't many bees in there. I worry about the brood getting chilled and dying. Is it safe or advisable to shake a frames-worth of nurse bees in there from another hive or are they likely to kill the queen?
There shouldn't be a problem shaking a frame or two into the nuc. The new bees wouldn't be trying to defend their own hive from an intrusion.
I would give them a frame of capped brood if I could spare it. This helps two ways. It gives the queen another frame to lay in and the nurse bees to cover it.