I can't give you any advice on what shows offer what you're looking for, other than looking at show bills. As far as things to do, start at home. Get people to come over and walk around your youngster. Have some kids playing nearby. Play a loud radio (this helps condition them to the PA). Find all kinds of things to sack her out with. Walk her near roads so she can get used to traffic. If there's a tractor where she lives, let her watch it work.
When you've got her calm in all these situations, haul her to some fun shows or junior rodeos or whatever horse events are in your area. Just get her off the trailer and lead her around. Let her get used to the sights and sounds and smells that are so much different than home long before you ever expect to show her.
Learning never stops