Once can never tell, how a given horse might do in shows. In each, you will have a different judge's opinion. Some horses stress at shows, some behave badly, even though they are angels at home.
However, I would take great
care of her hair and feather. No burned off edges if possible. Make sure she is in good weight. Teach her to stand four-square, head up and looking alert. Teach her to trot nicely by your side and turn properly in the other direction.
Make sure she is very used to travelling in the trailer. Take short trips and bring her home, often. Get her used to a great deal going on around her. If you live in a quiet area, then affix balloons, flags, coffee cans strung on rope, which blow in the wind and make a lot of noise. Play loud music, if it will not annoy your neighbours. This is all good practice for being out and about in shows or parades. Just make sure that she cannot hurt herself on anything you place in the area.