what does the heroine mean by sensing a ''potentiality for corruption'' ?

I think this relates to the protagonist relenting to the "male gaze": her sexuality becoming a comodity that she uses. This potential ‘corruption’, as it is phrased by the narrator, is in her own nature.

As she has lived a sheltered life, she has never acknowleged her erotic needs and desires. The Marquis's scocophilic gaze allows her to experience her erotic desires. Though the Marquis objectifies her, yet she seems to enjoy her objectification.