I've looked up the words beginning with "syl" and the word that jumped out more was "sylph" which means "an imaginary being inhabiting the air." Plus, with pokemon forums going about with leaks it has said that it is the lightest of all the eeveelutions, so I think we can concur that it is a flying type
After watching multiple youtube videos, I've come to the conclusion that Ninfia / Sylveon is going to be a Flying type. At least I think so. "Sylv"eon - it's very close to the word 'Sylph' which means an elemental being believed to inhabit the air.