a slut is someone who has many casual sex partners, who engages in sexual intercourse just for pleasure, for fun and for the sake of it.
sayu is a runaway girl, she offers her body in exchange for a place to stay, which is borderline prostitution (and i am against it) but she is not a slut.
if you call a non-virgin woman 'used goods', you need to reexamine your view on females and maybe yourself as well, fucking degenerate.