Exhibitionism, Crysta Style
There's a subtlety to Crysta's style of exhibitionism that deserves a word or two of explanation. You see, she craves public exposure and the humiliation that brings, but can never be seen as actively seeking such things, finding it more exciting for her partial nudity and resulting humiliation to appear "accidental".
By allowing herself to be discovered "accidentally" to be underdressed, Crysta lets the hapless witnesses feel a sense of shame for having peeked under her dress even as Crysta feels a tingly sense of shame at having her privates seen in this way.
Crysta seeks this form of exhibitionism / humiliation for the sexual charge it gives her whenever she's "discovered". But her behavior has an even subtler side: instead of setting out underdressed, she somehow gets caught up in situations that force her to reveal her (or her close friend Donna's) goodies to public view in a way lets her appear completely innocent. But innocent she is not -- she knows exactly what she's doing, and how far she's willing to go, and then ends up going just a little further in pursuit of her own humiliation.
Donna, meanwhile, admires just about everything about Crysta, and wishes she could be "free" like Crysta. To some extent, Crysta brings Donna along as her protégée, and to a greater extent, Crysta uses Donna, forcing her into humiliating situations (such as partial or full public nudity) for Crysta's own entertainment. There's only one thing more beautiful to Crysta than Donna naked, and that's Donna naked, sexually excited, and humiliated by her nakedness and even more humiliated by her own obvious excitement! In this way, Crysta awakens a powerful latent sexual energy in Donna, who reaches heights of excitement she never thought possible.