And then Silverlay died of a heart attack, the end.
 
@Background Pony #3CEB  
Read the rest of the comic.

@Background Pony #3CEB  
To give you a TLDR, Twilight encountered a spell that made a doppelganger of her. It’s original purpose was to steal her magic. But the clone had all of her memories, felt bad, and asked to be destroyed instead. Twilight wasn’t having that, because she used to have an imaginary friend (a twin sister, because Twilight is long on power but short on imagination, named silverlay) some stuff happened, friendship, yadda yadda yadda, and big bad evil guy was destroyed and we had a brand new sister for Twi. Also, she’s apparently a lesbian, and nopony even considered what that might mean for Twilight herself.
 
There you go.

@Background Pony #3CEB
 

 
There’s a whole comic to explain that before this one

“Original Character”