This is looking to be pretty accurate to the story in the comic that reveals how she came to the human world.

@Star Cavalcade  
This.
 
Was what I had in mind when we discovered her toy.

Another life ruined by our loving Sun Deity.

@Star Cavalcade  
Top kek.

No shit, Sunset murdered Alt. Sunset. Twilight was simply lucky Alt. Twilight didn’t remain at Canterlot High.
 
Consequently, if Cel knows nothing of “The World”, wouldn’t Sunset have disposed of Alt. Sunset outside of her view? :\

Sunset: “So I’m not good enough for you am I? Is that what you’re trying to tell me? She becomes a princess and what about me? Huh? What about me?”  
Celestia: (lowering her head)  
Sunset: “Well? WELL!? ANSWER ME, YOU IMMORTAL PIECE OF TRASH! LOOK AT ME WHEN I’M TALKING TO YOU!”  
Celestia: “You lack the discipline, Sunset. You’re not ready to become a princess.”  
Sunset: (laughs sarcastically) “Not ready? Me? I’ll show you not ready.”  
(notices the mirror and walks toward it)  
Celestia: “Sunset, what are you doing?”  
Sunset: “What does it look like, oh so noble teacher? I’m going to a place where I AM accepted as a princess. Where the denizens will grovel at the ground I walk upon and if not… I’ll just MAKE. THEM.”  
Celestia: “Sunset, I beg of you. Listen to me for your own well-being. The portal could tear you apart. There’s a reason why it’s forbidden.”  
Sunset: “How typical of you, Celestia. Always holding me back.  
(Sunset turns around)  
Sunset: (quietly) “Not anymore.”  
Celestia: “Sunset, wait. SUNSET!”  
(Sunset steps through the portal)

Seriously? You were recording every single action me and my friends were doing for the past few years and NOW you want me to become some kind of alicorn princess for your amusement?
 
I’m out of here. Good luck finding a chump stupid enough to go along with that.

“You’re not holding me back any longer! I’m not gonna end up like her!”