Can girls be cadets

Girl Scouts in the US in grades 6 to 8 are called Girl Scout Cadettes.

There are other types of Cadets, such as an Air Force Academy Cadet, and yes, girls may be that kind of cadet also.

Yes, Girls can be in cadets, for instance: Air Cadets, Army Cadets, Marine Cadets, Sea/Navy Cadets or cadets which are non-military such as Girl Scouts etc.