uh ... yeaahhh, well ... In my imagination ( hehe
) Gajeelīs necklace and Natsuīs armlet are signs for first rank guards
every princess hase a group of guards. Each group has a first rank as superior of the other guards.
First ranks are ( of course! ) the strongest ones.
And of course Mira has a reason to ask for exact those two to help and not Gajeel
I have such strange ideas sometimes xD