When you're an emperor, you could pretty much
R. Kelly a ho in the streets and just say "I'm the emperor, you should be honored." Well, ordinarily anyway. The empress dowager is the one who could actually get away with unusual shenanigans for now I suppose. Still, he has options, including the cold palace thing again of course. Executing her in particular might be tricky if not impossible presently. Marrying her off to some official might be doable. Pretty sure that was a thing with these situations, sometimes the harem is so large you never actually get around to giving a crap about everyone in it. If a woman in there catches someones eye, you could give her to them.