I doubt it is possible,a chastity belt is made of metal.
But is she's not too shy about it,she could show it,and explain she wears it by choice(for example,to help her stay virgin until marriage).
However,as others answered,I strongly advise you to not do it.She should not have to wear it far from your home,if you're her keyholder,for hygiene and emergency unlocking.
It wouldn't solve it,she would have the same problems when coming home,and not solve the issues about hygiene and emergency.
Sara2001 would it be possible to explain the airport security your situation?
I think so,too.If she explains it,it should not be a problem.