Board Thread:Boruto: Naruto the Movie/@comment-24992241-20160112202210/@comment-26037879-20160112232206

I don't think the games are considered canon, but to answer your question: seeing as though Sarada's an Uchiha, her nature transformation is definitely gonna be Fire Style; because the Uchiha clan is known for their mastery of the fire style, and like the Sharingan, it's kind of like their kekkei genkai.