A slogan like "Girls Rule" seems little more than a lie in this context. It implies that women leaders are respected, listened to, and rewarded for their hard work, talent, and intelligence - when that is clearly not the case. Perhaps the slogan "Girls Rule!" was created as a way of hiding the sad reality of gender inequality.
Riot grrrl spurred on an angry generation of female musicians to take up arms, as well as guitars, and fight back against the patriarchy, both in the record label boardrooms and across society in general.