At the shopping mall, some of the aliens were after Reika. So, if they had a group like that distracted by Kishimoto's finest features(her breasts), she could perhaps kill them. She did shoot some things in her second mission. Just because she enjoys staring off blankly, and doesn't seem too bright at times, doesn't mean she can't shoot a gun.

Typical male(alien or human, all species are the same): "Breasts! I see massive breasts, so I'll stare, there nothing else my eyes should be noticing."
Busty girl with gun then shoots him dead, he not noticing the gun, or thinking clearly, overwhelmed with his male hormones.

See? It can work.