I don't get this conflict it at all. Why is she suddenly decided that she is just sex toy for him? There wasn't a single clue to lead her to that conclusion, besides maybe his over the top sex-drive, but it's not like she was being neglected or something. He was considerate of her and gave her more than enough attention not only in terms of sex.
The reason for drama is pretty good itself, but realization is kinda meh and feels too forced