Answer:
Girl Scouts of the USA and many other Girl Guide and Girl Scout organizations around the world (members of the World Association of Girl Guides and Girl Scouts or WAGGGS) do not use a rank system such as Boy Scouts use.
Instead, they are placed in troops or groups based on age level or grade level and have a choice of Insignia (badges and other awards) to earn. Girls "Bridge" to the next level once they finish a grade or reach a certain age.
The current (2011) Girl Scouts of the USA grade levels are:
Girl Scout Daisy - grades Kindergarten and 1
Girl Scout Brownie - grades 2 and 3
Girl Scout Junior - grades 4 and 5
Girl Scout Cadette - grades 6, 7, and 8
Girl Scout Senior - grades 9 and 10
Girl Scout Ambassador - grades 11 and 12