I was a sea cadet for many years and I loved it. Assuming she doesn't harbour desires to join one of the services, or to do activities closely associated with one branch or another, such as sailing, flying etc then I'd say the main difference will be in the local units. I'd suggest she visits them, she can go along and get a feel for them without committing. Largely its the enthusiasm and interests of the adult volunteers that make a unit rather than an, and its important she 'fits' that feel to get the most out it of her time with them.