
I'm not the op, but the way i interpret it is that it's a smartphone that has the game thus her ability to manipulate them, but as the other comment said, she(Yvonne)probably isn't familiar with the hard mode, this is because the hard mode was where the Penelope had to try to get the affection, not the og Penelope (in this case Yvonne)

Page 7 on the 169 chapter. We saw the mirror up close. I can be wrong but that looks like the screen of a phone. Like a long rectangle with a top corner missing.
From what I remember, we never saw a clearer image of the mirror.
I would need to re-read the entire story to be sure and gather more evidence but no time for that live xD
Sorry for my english, it is not my first langage
Wait, I’m stupid. I just realize that the mirror is a smartphone screen.