I find not the local shows round here dont have much for pure bred Arabs, what did you want to do in hand or ridden? Is she registered with the Arab horse society if yes you can enter the shows they run, have a look on there website and there are Arab horse show groups all over the country, where are you ?
If she's old enough, you can do Veteran classes. Best Turned Out and Best Condition would also be fine, plus any fun classes that the show offers eg Prettiest Mare. Some shows have a Foreign Breed class and she could do that too.