Step One is to understand whether she was balking out of FEAR or out of CHALLENGING YOUR LEADERSHIP, which question I asked of you in my first post. You won't EVER be able to respond properly for your horse if you don't assess their reason for balking (or whatever). Furthermore, you'll ruin the horse, because scolding for fear is so destructive to the horse, & puts your relationship in the negative numbers.
Sometimes, also, it's flat-out CONFUSION, based upon IGNORANCE of a fact(s), & the confusion is swiftly followed by FEAR, because it's scary to be confused.
I'm not looking at the horse as if he's a human at ALL. Apologize to your horse when appropriate, you bet!
So, again: why did she refuse to proceed?