I Truely believe Salem and Cinder are parallels of eachother
"the girl in the tower used her power and led many warriors to their deaths"
the solitary captive whom wore a crown made of quiet tears ,
the faulse savior fought for glory, not for what was real,
thus the girl who waited for her faulse savior died inside the stone,
A queen walked out to claim the world her own.
Who shares the same core motivations to Salem , a desperate desire for freedom, and an unchecked obsession with power( Salem grew a family and turned to ozpin to help her rule a planet as gods)
Salem was locked away in a tower sence she was a child, and Cinder at the mercy to the poeple that "adopted her"(including Salem)
Regardless Salem only views Cinder as a tool while giving her "strength" to size control, not knowing the Grimm is slowly taking over her autonomy.
I think the reason of the Grimm arm is not only to kill cinder if she betrayed her or simply no longer became useful, but to literally take cinder over to the point where Cinder is Entranced or Possessed. I could see Cinder becoming the next "Girl in the tower" this way quite literally
Cinder escaped her childhood tower only to willingly walk into Salem's and possibly take her place.