well you will need to guess more than the element =P she has three types, attacker, tank, healer....Hopefully teddo can produce a great guide. I definitely never got my dragon to where I wanted her to be. Settled for Shadow Attacker.
Looks like guild war will probably be fire element judging by the boss sprite. Also, the story event is a rerun of the "Romeo and Juliet" event and a potential new story continuation just like how Robomi event did.
I just wish Cygames bring back some older story event. I really want Selfira and Aster.