Yes this character is one person, but rather two genders...or is it none?

They can form to be any gender, or even none.

They prefer the They, them, theirself, etc.

As they are an ethereal being of neither side of a single spectrum. Rather they share what a flower could, they could mate or be mated and yet can also deny to be mated with all together.

Dentro is named out of a purple/white flower that is commonly found in some forests and sprawls out similar to wings with it's petals.

Yes, you can have sex with them...they can form into both or neither gender at will, they can also cut off any feeling to themselves as "pleasure" thus you can't just lure them in with that alone, they are difficult but if asked rightly then the said sex would be godly compared to most.