I'm an idiot for even bothering...but...
It can't really be working for you if your only claim to being useful is an ambiguous ranking (shared with a several no-name or named bit characters and everyone else in your age group with the exception of the main character (whose very existence lessens its worth)) and speculation.
I mean come on, what do you think "USELESS until proven otherwise" means? A paper rank is not proof, nor is a argument that she hasn't used her full abilities. The manga isn't named "NEJI", "ROCK LEE", "SHINO", "SAKURA", "SHIKAMARU", or even fucking "TENTEN" either and they've all shown a greater degree of usefulness than our favourite MOE throwaway character.
When she starts busting out these skills that you think she possibly probably kinda sorta might have, then she'll rise from the dregs of uselessness.