In the first Iczer series, Fight! Iczer-One, it is one young girl with a giant robot. I do not have the second Iczer series known as Iczer 3. In the third Iczer series, Iczelion, it is a group of young school girls in body armor who must save the Earth.
In both of the series, there is usually a resistance on the part of the young heroin which is not overcome until the heroin in question realizes how important she is to the survival of Earth.