"Thanks, Spike!" says Fluttershy, and heads off toward Sugarcube Corner.

"You're welcome! Good luck!"

When she reaches the garishly decorated building, she enters the door at a run, sliding across the floor and coming to a halt in a sitting pose. 

"Twilight! Pinkie! Come look, I met a new pony!"

oh no

"Oh! Welcome to Ponyville! What's your name?" says the purple unicorn who is presumably Twilight.

Pinkie Pie doesn't say anything, just narrows her eyes suspiciously at Abrogail. Her eyes, apparently moving independently of her head, perfectly track Abrogail's every movement while she continues to stuff her face with cake.

"Her" Infernal "Majestrix Abrogail Thrune, Queen of Cheliax, blah blah blah and so on, presently in exile."

"I've never heard of anywhere called Cheliax—and Princess Celestia is the ruler of all ponies."

To-do: find out how true that actually is on a scale of Taldor to ten.

"Yes, it's probably very far away. I wanted to see if you could help me figure out where I am in relation to anywhere I know. And I wasn't originally a pony. I was—" she makes a Silent Image of her human form.

"...why don't we take this back to the library? Fluttershy, your job is to make sure there's still some cake left for the Princess tomorrow."

"...okay..."

"So, what exactly do you think happened?" Twilight asks Abrogail when they're back at the library. This is probably an 'ask the Princess what the fuck' type of situation but the Princess won't be here until tomorrow and Twilight's curiosity cannot in fact wait that long.

"I was the queen of a country on the planet Golarion. Ponies there don't talk—actually, the animals we call 'ponies' only look vaguely like you—like us," she corrects. There was a war. I was—magically imprisoned—and when I regained awareness I was four-legged and furry and standing in a field a couple miles from here. I thought at first I was in Nirvana—"

Twilight now has additional questions. She's going to interrupt before the list gets too long to keep track of.

"Hold on," she says. "What's a 'star-that-moves'? Stars don't move—well, the firmament moves, but they're attached to the firmament, unless you mean shooting stars, but I don't think you could live on one—if you could even live on a regular star, which—"

"Well, that answers some of my questions about this place," Abrogail says. Namely that they probably aren't on the Material. "A planet is an enormous ball of rock, so big that it seems flat from its surface. They orbit their sun like so—" Silent Image of Golarion's solar system (with the planets dramatically magnified).

Abrogail isn't really considering the possibility that Twilight thinks her world is flat and is wrong about that. There isn't actually a time in Golarion's recorded history before it had someone who could teleport to space and instantly verify its shape; she doesn't know this to be something that societies without the benefit of teleportation habitually get wrong. (No doubt some peasants back home get it wrong anyway, but Twilight is supposedly a wizard.)

This is all very fascinating but Twilight is distracted by a comparatively minor aspect of the situation.

"Could you do that illusion spell again? I want to watch you cast it."

"No; I have a limited number of castings per day and at this rate am likely to need all of them."

"Aww." Unfortunately that makes sense. "We'll have to exchange spells later. Anyway, that's definitely not how our world works. Princess Celestia moves the sun, and Princess Luna moves the moon."

Wizards in this world just share spells??

—if the thing about the sun is true, then probably this world is in fact some kind of divine domain or enormous demiplane, with 'Celestia' and 'Luna' as the gods and/or archmages responsible. (This would be a ten on the Taldor scale.)

"Do your people die of old age, and does anyone know what happens to their souls when they die?"

"We do die of old age. Well, except the Princesses. I'm not entirely sure what you mean by 'soul', but I think dead ponies are...dead, they don't go anywhere else that we know of."

"Hasn't anyone ever tried scrying them?"

"Doesn't work. Scrying spells are finicky over long distances even within Equestria, though, I wouldn't expect it to even if there were something to see."

Mortals, then, with an unknown relationship to the afterlife system and suspiciously bad scrying. Maybe they go to the normal afterlives and Celestia just blocks scrying lest any of her little ponies be traumatized by learning about Hell. Abrogail isn't going to tell them either, though for entirely different reasons.

"Anyway, I'm trying to figure out what plane I'm on, either to try to get home or at least have a better idea of what to expect here. You've helped me narrow it down a lot but this world still doesn't match any of the planes we know of."