Girly girl is a slang term for a girl or woman who chooses to dress and behave in a traditionally "feminine" style, such as wearing pink or floral dresses, blouses and skirts, wearing make-up, talking about relationships and other activities which are associated with the traditional gender role of a girl. It may be considered derogatory by some.
The term has become more common as a term of disdain or abuse among some people, particularly tomboys and some feminists, since the "second wave" of feminism in the 1960s and '70s, after which unisex clothing and/or behaviour started to become more prevalent among females. Others have defended girly girls as they have chosen to be the way they are and their lifestyle is based on choice.