What was the inspiration to make this AU?

The inspiration for this was inspired by a Steven Universe horror AU I can't remember the name of.

What happened to Y/N's Mother?

Y/N's mother was a part of the Diamond Authority as Blue Diamond, she was created by White Diamond to represent Tragedy and Chaos, but when Pink Diamond showed Blue Diamond, Blue fell in love with Earth just like Pink. When they couldn't convince Yellow and White Diamond to not colonize earth, Blue and Pink turned to drastic measures. And the rest was history. 

  Will Y/N corrupt at some point?

Yes, and it will be drastic 

Will the characters/story be the same as the original? 

Besides some physical changes to some of the characters and some of the story being rewritten (ex. how Black Hat fell in love with Y/N), plus giving a backstory to Black Hat, then yes.

Is Y/N Steven's aunt?

It's complicated, but yes, Y/N is Steven's aunt

(A/N: If you have any questions, please ask them here!)