Her Mind, His Manipulation - Mabel x Bill

The summer after graduation was supposed to be simple for Mabel.
But with Dipper away on a summer internship and the future looking uncertain before her, Mabel Pines returns to Gravity Falls.
Back to the old Mystery Shack, back to the people she was once so close to, and back to the familiar strangeness she once called home.
It should feel comforting.
But it doesn't.
The nightmares she's carried since that summer when she was 12 follow her back. Except... they're fiercer now. More deliberate. Less like memories, and more like something watching her remember.
And the worst part is, this time she's alone. At least until she isn't.
The source of her fear being back in this town.
Bill Cipher.
But Bill isn't supposed to exist anymore.
They defeated him. Right?
And yet, in the quiet space between sleeping and waking, he feels closer than ever-
like a joke only he understands, and she's just beginning to hear the punchline.

-This is a Mabel Pines x Bill Cipher Fanfiction
-This is also my first ever fanfic I've written so please be nice :)
-I'm very much open to constructive criticism/ feedback!
-All characters belong to Alex Hirsch