Basically, Otaku was never actually dating Shirahoshi.
Later Shirahoshi then talks to our Gyaru to thank her and apologize for losing her powers because of her.
She tells her that she and Otaku were never dating since he rejected her and tells her she should go talk to him, she thinks they’d make a good couple.
The gyaru goes to look for Otaku at the crime scene, where it turns out he was picking up the pieces of the crystal ball because he was determined to take it to get it fixed.
The gyaru kisses the otaku (finally) and throws the pieces of the crystal ball into the river
And I’ll let the ending speak for itself.
https://mangadex.org/chapter/54376014-a8c3-4757-9a8b-3939f639dac9/4
Even if it is someone who isn't your "soulmate."
You can still fall in love with that person, right?
That...
It means you are the person destined for me.
Right?
My Gyaru (Uranai-san)
... Yes!
Even Uranai-san, with her predictions, can be wrong sometimes, right?
That's right
Because i am ...
Phony Fortune-Telling Gyaru
END