Back in episode 17, when Meroron seemed to sacrifice her memory for Purirun's sake, there is a tweet from a father, who is a dedicated Precure fan, who complained that it is inappropiate for a kid show to show that someone can sacrifice their own happiness for if that means other person will be happy.
Today episode feels like Toei anticipate that kind of complaint and show us that Meroron doesn't actually sacrifice her own happiness, afterall.
That is to say, I don't think people should consider the worst out of Meroron (whether they consider it as a bad thing or a good thing),

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because Toei has no interest to make Precure a bad guy, and they know parent will complain if there is ever a bad Precure.
There are many options for why Meroron is keeping Purirun away from Uta & friends. Ranging from she is afraid the spell can be undone if Purirun remembers to she doesn't want Uta to blame herself if Uta knows that Purirun lose her memory in order to protect Uta.
I wish Zukyoon mystery would stay longer, and this episode kinda deflate my hype quite a bit, but I guess this arc has to end around episode 21-24 for the next wave of toys.