Best place to put it.
Reminder we could have had a *six-episode arc where Thorax tries to get a treaty going with the ponies and his hive and they enter a very uneasy alliance where they donate some love to the hive in exchange for not plotting against the kingdom.^ At first it doesn’t work so well because Chrysalis is the ‘hunt, not be fed’ types and keeps plotting anyway until a threat they can’t defeat comes up and the ponies(notably reluctantly) help them, leaving them all, including the queen, shocked. And the climax of this arc being where the hive returns that kindness, as what seems to them as foolish, unwavering trust actually causes them to develop a sense of obligation and camaraderie to their allies.
There could have been a day when Chrys would be called into the summit of princesses and they welcome her like one of their own, no brainwashing required.
Only physical changes are less holes in their anatomy from being fed a sustainable amount of love. And maybe the flowery, bright version of the hive can stay if they upkeep it a bit. Doesn’t look cured, it looks abandoned.
I don’t now, and never did hate the idea of good changelings.
I hate the idea of turning the changelings into crystal ponies.
*chose this length because these writers hate stories with proper care, time, and structure.
^this solution is mainly so the ponies have to give up something more than time and few parties to keep the peace and don’t have some cure-all to make former enemies more convenient to them.