Fionna the Human is a separate character from Finn the Human, female in-universe from the beginning. Tag "male:gender change" is inapplicable to that case if she is depicted as female/dickgirl.

However, for genderbent version of Finn the Human - once again, separate character from Fionna the Human - that tag would be needed.

So, a dilemma. Is this a genderbent Finn, or non-genderbent Fionna?

Base +31, FerKing +7

Well, it's got tits, but it looks more close to Finn's origional design than Fiona, so I'm inclined to think it's a genhderbent Finn.

Base +6, SomeUne -6