Poor you for experiencing this on your first time out together.
The best thing to do is just forget it and look forward to your next show together. Was it slippy? Did you have studs in? If not, then this is something I would consider.
Sorry if this has been said, but I haven`t had time to read all of these posts. Catching up after a very upsetting week.
Make sure that you have a practice at home to get both your confidences up. She obviously is a lovely mare, so enjoy yourselves.