"And so you see, darling, I only needed evidence," Rarity said. "I knew it was Lady Trottingham all along."
"But how?" Twilight asked. "The evidence ... yes, it makes sense, perfect sense, but how did you know in advance?"
"Vanity. I understand it much better than you do, dear Twilight. A curse of my trade, though a useful one."
"Vanity?"
"The Star of Zebrica. Such a pretty bauble, with such wonderful colors. Swirls of green and blue, and in the heart a speck of ebony. Said to be the only shed tear of the —"
"But how did it tell you who it was?"
"If you stole it, perish the thought, you'd examine it, yes? We'd find you hunched over a microscope, peering at the center, trying to see the meshing of tiny gears, seeing how blind nature made such beauty."
"... I guess. Yes. It's fascinating."
"Indeed. Because you are you, darling. If I stole it, you'd find me sketching, hoping to make something that reflects its beauty. But, anypony who'd be ... small enough to actually steal it, would want it for something much more base. An adornment. A trinket. And, they wouldn't want to wait, oh no. They would want to see how it gleamed on them right away. As soon as they can steal a moment's privacy. And so they'd pick the colors of the costume to match. Green. Blue. And a touch of black. And who did we see in a simply stunning ensemble of olive green, sea blue, and a jet accent, mmm?"
"I can't believe it came down to dresses. I'd have never seen it."
"Oh you mustn't fret, darling. You study magic, and none can match you there. I, on the other hand, study ponies."
"Didn't you live here?" Rarity asked. "How can you not know who anyone is?"
"I — I never paid much attention to all of the politics stuff," Twilight admitted. "I hated it. Most of the time I was in the library, you see, and I was —"
"— That will simply not do, darling. You are a mare of substance. A true lady. Friend to the princess. You must be able to read the crowd. And how can you do that if you don't even know who the Press Secretary is?"
"I thought you didn't know who she was?"
"I didn't know. I saw."
"Saw? Are there nametags? Omigosh, did we miss getting nametags?"
"No. Darling. Darling. Look. Just look. It's obvious. Look at her. Fresh hooficure. Immaculate mane. Brushed coat with tasteful dyed accents. Understated and expert makeup. Her morning toilette must take upwards of two hours. And yet her dress is plain. Of the finest of silk, no doubt, but plain. Why? Money? No. Look at that brooch. Jade and silver, inlaid with jet. Expensive. Ten thousand bits if it's a penny. So why a plain dress?"
"Maybe she likes simplicity?"
"No. No. Nopony with eyebrows plucked with such, ahem, psychotic precision is fond of simplicity. It's all part of an effect, my dear. She plans to talk to a number of ponies who are likely to be dressed fine, and wishes to appear suitable but non-threatening. A professional of some sort used to dealing with touchy clientele. But with this little soirée being as exclusive as it is, it is safe to assume her job is something to do with the media. I thought reporter, but obviously she isn't."
"It isn't obvious to me."
"Really dear, look at the pony she's talking with."
"He's, um ... short ... and, really quite shaggy, and ..."
"The necklace."
"Silver and amethyst. It doesn't fit him."
"It's also the chain of office of the Cabinet Secretary. And look, he's talking to her without that guarded expression officials get around reporters. So. Not a reporter. That leaves someone in public relations. The press office, most like. And look. She's relaxed, not apprehensive at all. She's talking to the head of the whole of the Civil Service, and she's not nervous at all. So, of high rank. Highest rank in the Press Office is, of course, Press Secretary. And there you go."
"Now that you lay it out like that, it does seem obvious."
"It's a curse."