And then Flurry Heart was made

Cadance didn’t do anything princess worthy until becoming empress of the Crystal Empire after this episode. Prince Blueblood shows many others with such titles exist. Twilight was too young/caught up in her studies/distaint after moving to Ponyville to care nor follow such political nuance.

@Background Pony #C58D  
le animation errors.

@TexasUberAlles
 
Wasn’t the princess in this book an alicorn? We know from Twilight’s Kingdom that there are only four of those at present.
 
Platinum may have been a princess in her days, but in modern days the title seems to be held by alicorns. At least I don’t remember seeing otherwise.

@Bonk  
There can’t be foreign princesses  
@Background Pony #C58D  
‘‘Princess’’ clearly seems to be a unique title only the four alicorns share  
Have you read this book?  
 
There’s something in it about a dragon, a kingdom falling, chaos reigning…
 
Maybe you’ve seen this stage production?  
 
Platinum was even a local gal.
 
Foreign princesses are already an established fact of FIM, and all it really takes to explain “Mi Amore Cadenza” being unknown to Twilight is that Cadance was one of those foreignesses who never had any occasion to use her formal name around the small child she was foalsitting. If anyone consistently refers to themselves by their full name with all their degrees and professional honorifics and guild associations when speaking to children, chances are they’re not going to be allowed to speak to children for very long.

Anger short circuit. She was so mad at Shining that she wasn’t thinking.

@Bonk  
Perhaps that’s “every princess in the context of the magical superrace of ponies”.

@Ferrotter  
@ImRaidAccount  
Headcanons accepted, or at least very seriously considered…

@Ms. Harshwhinny
 
It’s more that she already knew of Cadance being a princess, and I assume princesses are like presidents or governers to their land so Twilight not knowing about all and only three would be pretty strange. From there, it’s just basic deduction

@Background Pony #D2A2
 
There can’t be foreign princesses because in the season four finale, Tirek thought he captured every princess until he found out about Twilight, and Celestia confirmed by making that plan that there were only 4

Who knew? At the time Cadenza could’ve been Cadence’s sister.

For all we know, there could be foreign princesses. We never did learn the titles of the Saddle Arabians, after all. And who knows what other groups there are that might use the title.

@Ms. Harshwhinny  
“But you’re a princess, and I’m just a regular ol’ unicorn.”
 
I just found it hard to imagine how vividly she remembers her foalhood memories with “Cadance” (Whom Twilight herself referred to as a princess in the show.) But when a Princess “Mi Amore CADENZA” pops up to marry her brother, She draws a blank. lol
 
It was never shown in the series that Cadance and Shining Armor shared the relationship they do in the non-canon comics, but one simply does not marry unless there’s some sort of relationship there… or you’re thinking with the wrong organ. >_>

First of all, she’s so much of a shut in that she doesn’t pay attention to any of that crap since it’s not in a book.  
Second of all, she probably just referred to herself as cadance when she was babtsitting her.

@PonyPon
 
Doucheland. Lovely place

@ImRaidAccount  
4-Ruler of an as-yet unnamed territory.

Only 4 princesses remain in Equestira and soon to be a fifth one

@Background Pony #C58D  
Option 3: Prince is actually is name.

Perhaps it’s to lampshade just how out of nowhere they were.

Maybe Sapphire Shores sticks Princess title grants under the seats of her audience every once in a while.

@Mildgyth
 
No it probably isn’t. “Princess” clearly seems to be a unique title only the four alicorns share.
 
As for Blueblood, two options:
 

@ArrJaySketch
 
Considering the existence of Prince Blueblood, your suggestion might be true.

She knew said princess by a different name. Besides, their are other cultures besides Equestria with kings and queens, so there’s bound to be more princesses out there. What if Shining had been marrying the Princess of the Hippogriffs or that Queen Amidala look-alike?

@ArrJaySketch  
But yeah, the “princess” part is a dead giveaway.
 
…unless Celestia has a habit of making various nobles “princesses” in title only.

To me, it meant that Princess Cadance never referred to herself that way, nor did anyone else. It always struck me as part of Queen Chrysalis’ imperfect guise.