Onyx could actually benefit from the program in the book "Click to Calm-- healing the aggressive dog" by Emma Parsons. I have never thought I would give this a try, but.. wow. I had no idea something as simple as a clicker could make a dog actually begin to feel in control of a situation in which they normally feel NOT in control and at risk.
While the program is begun in your livingroom doing simple OB Onyx already knows, in a room she already knows, with zero distraction... in a few weeks, doing a lil click-n-treat(use special, high value treats in these distraction zones)in a very mild outdoor situation, then later after a few weeks in more stressful situations, thinks: "Oh, man.. clicker stuff is happenin'... whoa, I know what THIS means.. time to WORK! Just like at home in my very own comfy livingroom with Mom, when I gotta sit and down and do a watch command and stay and stuff! Hey, wait a minute.. Mom is askin' for one of those things right now I think.. oooooooh, it's SIT! I do WAY GOOD at sit! A snack is comin'! Yummm.. great!! Ok, next is... what.... stay? Down? What's next, Mom? " etc. Her sense of control comes in the idea that she is winning.. succeeding..easy OB she knows. Plus, The clicker takes the handler outta the pic-- our emotions can add to the frazzled dog's responses. Plus-- and this is BIG-- clicker means working.. not bad stuff happening! Working = better focus.. gonna get good stuff! Doggy also thinks "I went to a slightly stressful place today, and.. hmm.. nothing happened bad, I just worked hard, got praise and snacks, all good stuff happened, plus I was in control."
Read the book, then begin the program with Onyx. Weirdly, this can help the dog feel in control, gradually, in new situations in general. Then, move this-- clicker OB training, simple usual stuff she knows already but with clicker-- into gradually more stressful situations.
Another technique very useful (but also takes a loooonnng time) is click-and-treating in the midst of slightly stressful situations for when she does ANYTHING that indicates calmness-- finally rolling onto her hip while in a down position, sighing, etc. at the park while watching noisy, active kids playing soccer, for instance.
The clicking removes conflict.
I honestly have never been a big fan of the clicker idea... but seeing it in action is amazing! This kinda program takes a long time. But, it can help build confidence in her, distract-then-make-positive -associations-in-stressful-situations, and mark GOOD behavior (in her mind, it becomes GOOD behavior to relax) in these situations.
Wishing you and beautiful Onyx the best!!