— PLEASE REMEMBER THAT ART IS SUBJECTIVE & ANY OPINIONS GIVEN HERE ARE MY OWN —
I'm more than certain that I am not the first person to think of this. Still, it's a fun little theory so let's have a look.
First off — how old is Cinder? Honestly, we don't know. We know she can pass for an upperclassman apparently & if I recall correctly, Monty once said she's not much older than the main characters — gotta love that vagueness. So a decent age range at this point is early to mid twenties.
Now, let's take a look at her choice of weapon — before acquiring Maiden powers, naturally.
Two swords that combine to form a longbow which can fire explosive arrows — it's also a gun! If that doesn't follow the outline of a Hunter's weapon, I don't know what does. Despite being only a few years older than the main cast — she already is rather skilled in combat — in some cases more so. There is no denying that Cinder has had extensive combat training — the kind that takes years of practice to master.
She got that training somewhere & over the course of many years. Cinder being a former Huntress would answer a lot of questions. It would explain why she was always several steps ahead at Beacon. She already knew their tactics, response times & how they would act in a given crisis.
Is it true? I have no idea — but it's an interesting thought.