They get a few defining features each, but Brittani Slocum and Misses Montana, New Mexico, Ohio, and Arkansas don't get their own full storylines. In fact, the latter four are so interchangeable that they're only called by their state names. Toward the end, they try to use real names, but it doesn't work because they're all named Caitlin. (37.39-49) Apparently new moms had a name creativity drought that year.
Basically, this group is in the story to be a chorus of additional voices—often the voices of more typical beauty queens. Well after the other beauty queens start to change, they're still playing stereotypes:
"On her way, she passed Miss Montana and Miss Ohio, who were lying on their backs in the warm sand. They'd positioned scraps of silvery metal from the plane's wing at chest level and were using them to reflect the sun.
'What are you doing?' Nicole asked.
'Working on our tans,' Miss Montana said." (16.1-3)
Oh. Helpful, for escape and stuff. Yikes.
So, these girls allow Bray to keep the humor going in the later half of the book, when many of the main characters have deepened and aren't clichés anymore. But these girls change too—as a group. They fight the black shirts together in the battle scene, and as we find out in the final montage, will grow into pretty impressive women.