’Cause all of her friends are in this dimension.

@Background Pony #0F8C  
she is always cute

I’m still hoping we see her go back to Equestria someday. She’s cuter as a unicorn.

@Ilsor  
I guess there could be more magical trouble roaming around. wish they could mention that.  
@PonyPon  
But it’s Human Sunset’s home. That would be a problem if she showed

and she has home in human world?

@Ilsor  
Yeah, when magical hate plagues threaten.
 
Though I guess that at least sounds like a partway noble cause and excuse.

Good question, statue portal.
 
I guess this must be her home dimension now, in the interest of keeping this franchise separate from the main one.

Rainbow Rocks clearly showed that everything will just fall apart without Sunset’s intervention, and she knows that.  
That’s why she’s staying.
 
@TwilightVelvetSparkle  
All of my yes.

I must say, this movie makes me wish for Sunset to be a new main character…I mean, that’s practically what they set her up as.