We are Catholic and my 13 year old daughter and dad went to a purity ball at our parish last year. It was a formal event. The husband wore a tux and the daughter wore a cute poofy pink floor length dress with a matching hair wreath, white tights and pink Maryjane shoes. To add to her purity and innocence, I did a cloth diaper and pink rubber pants on her under her tights. She looked gorgeous in the outfit and pledged her purity to dad until her marriage.
She told me afterwards that quite a few of the other girls there also had a diaper and rubber pants under their dresses as well, so she wasn't the only girl wearing them.