Quote Originally Posted by Mizuchi View Post
Something I mentioned several posts back. You don't need earth or fire to make acid. Acid can be made from water, which is only made of two ions. If you have a high pH, you have a low amount of OH- and a high amount of H+, thereby making it acidic.
If you're being scientific about it, sure. Whose to say Kishi is being scientific about it.

She specifically states she has two Bloodline Limits, and it's called Vapor Style: Solid Fog Jutsu.

When a jutsu starts with "Suchandsuch Style:" the suchandsuch is the Element. So one can assume that Vapor Style is a combined element.