Annabel answered everything so, I wont' even go there.
I just wanted to say that I am floored that your coach wont' be of any assistance to you. That is bizarre. Just because she is competeing against you doesn't mean anything. You are her student, her protege, in her tutelage, her care. She should be there for you. Most coaches go with their students of possible, and they are paid a fee, as if they are giving you a lesson.
If this is just a schooling show, I think you should go for it. It's about learning, so who cares if coach not there or not helping (though it lowers her in my eyes). Check it out, observe, see how it feels to be in that arena, hear the bell and keep your pattern in your mind. Good practice.
I get insanely nervous, but I actually prefer to have my test memorized than have it read to me (which is permitted at schooling shows in the lower levels). But, it's amazing how it all comes back to you.
I practice my test a lot, unmounted, on the rectangular living room carpet. I walk and trot it myself, as if I am on a horse, and visualize how I will prepare for each movement. I literally hold my hands as if holding reins and do the little adjustments of finger/wrist and core muscles that I owuld be doing as I half-halted, started a free walk, came out of the free walk, came to the halt, whatever . . .. Do it so many times that you know that pattern inside and out.
I memorize it like a visual image in my head, something like the dancing patterns of bees communicating to the hive!