This is a little off topic but still pertains to team composition and Ultimate difficulty clearance.

In Yata Garasu advent event, DMM first implemented Event Missions. Out of the numerous rewards, the hardest mission, "clearing Ultimate difficulty with only himes rarity R or below", has the best reward of a Dragon Eye shard piece. Are you planning about it?

As for your original question, if I were you I would search up DMM wiki to see the damage range of Yata Garasu. If she has high damage Rage burst or something similar, I would go for the Water team, just to capitalize on the natural elemental resistance.