Reactive, unpredictable....just 2 words of many I would start to explain spooky as.
What you describe as jump in place to me is more startled but thinking...
Spooky horses react then think...they move first.
Thinkers, think it out and decide if it is something to run from.
Your Moonshine sounds a bit of both...lets you know something is their, but uses the brain to reason is it worth running or reacting from.
The safer mount is the thinker in my book and worth their weight in gold.
Your trainer, I'm sorry sounds confused that a horse who needed to be taught that going roundy-round in a ring setting is fun, challenging and exciting thinks that being a bit reluctant, opinionated and balky to the same roundy-round is spooking...she needs a serious education of what a wheeling, reactive mount is all about.
Horses get bored doing the same mundane things every ride...so change it up.
Moonshine I bet likes to explore and see, do different things...investigate and get into sillies when allowed.
Go on a trail ride, go ride in a different area of the field/paddock not often seen.
Make the ride something to think about, not just mentally plod around about...
That mental stagnation can actually create a spooky horse when the horse loses concentration then gets caught by surprise a few times they learn then that kind of reaction unnerves the rider and suddenly they aren't ridden so much...oh yes, do be wise to how a thinker can become a habitual spook to get out of working.
I would classify Moonshine more as settled mentally, not letting much set her off but to look at it first, then react gently....
If though that settled mental ability horse ever truly spooks or tells you it is time to move on...you go immediately cause the horses sense of self-preservation will safely whisk you away or leave you to fend for yourself the imminent danger.
My trail horse is a thinker, doesn't rattle easily...but when he hits alert status of quiver and tense...he has my attention.
If he says we gone, catch my dust!!
If he says we face it down...we do.
Moonshine sounds much like my boy...