characters were going to have different parts of their personality emphasized for single episodes
Flanderization is more of a permanent thing. Basically what I'm saying is "Just because Rarity was a little bit of an extra drama queen for one episode, for a single gag, doesn't mean this is a permanent change."
But that's the thing. Rarity was never a drama queen to begin with. She was the one who stayed calm when
other people were overreacting, and in some cases outright mocked them for doing so. Having her be a drama queen is not showing a "different" part of her personality. It's contradicting a well etablished premise of her character. Kidnapped by diamond dogs? Oh, is that all? Need to confront a dragon? Surely you jest, darling, any dragon worth his hoard will surely be reasonable. Need to face doom and horror, and certain death? Well, if you insist, darling, but you simply
can't face certain death looking like that! Let's spruce you up just a little. Go out, facing the end with a sparkle in your eye!
That's Rarity.
Having her be helpless and whiny is like giving Bambi a bazooka. It might be good for a cheap laugh, but it's totally contrary to the point of the character. Once you give Bambi a bazooka, he's not Bambi anymore.
But since so few people seem to understand Rarity, let's work with a better example: Fluttershy. She's been getting it way worse than Rarity.
Remember Fluttershy? The
shy one? The
quiet one?
Here's
Fluttershy's introduction from season 1 episode one. Twilight says hello, she jumps. Twilight introduces herself, Fluttershy can barely say her name. And what brings her out of her shell? A
baby dragon. Because she loves animals and children and lovable, cute things.
Here's the infamous
Fluttershy 'yay' scene. She's with a close friend, Rainbow Dash, who she's known since before she got her cutie mark. It's as close and safe a relationship as she has, but even so she still with all her effort and both lungs full of air she can't bring herself much above a whisper. And even that, she worries is "too loud."
But...bring in one single out of character freakout in Best Night Ever, "You will love me!!!" and now
every single episode in season 2 features a Fluttershy that doesn't match who's she's been for the 25 episodes prior.
* She spent episodes 1 and 2 being "Flutterbitch" compliments of Discord
* In Lesson Zero, she becomes
kung-fu chiropractor, literally yelling and screaming as she does. At the end of the episode, when they went to confront Celestia on Twilight's behalf, she was in front with Applejack,
bashing the door down before Rainbow Dash even entered the scene. Fluttershy?
Bashing doors down? * And now in Nightmare Night, when Twilight and Luna go to her house, she
screams at them rather than answering the door.
What, seriously? Fluttershy, the quiet, shy one who can barely say her name and can't say "yay" above a whisper, the Fluttershy who loves animals and babies...is now yelling at children who come to her door to trick or treat?
Rarity was out of character for one episode. Fluttershy has been so badly flanderized that at this point, more people probably associate her with yelling and freakouts out than they do with anything she did in season 1.