Good for her!
I knew a girl in college who had lost one of her hands in an accident when she was a young girl. One night a bunch of us were hanging around, drinking beer, etc., and a guy asked her, “Well, then how do you shave under your arms?” Without batting an eye, she said, “I hold the razor in my hand.”
Beautiful girl.
This girl, and the rest of them for that matter, are judged on interview skills and talent, fitness (used to be called swimsuit), and poise.
Having an arm, or not, is irrelevant. There have been some Miss Americas who are not beauties in the traditional classic sense.
These girls also rack up some serious scholarship dollars.