Hi Addie,
As Zuzannah said you can't change gender in game, nor here at website.
And usually Support is reluctant to changing gender. The only situation they allow it is right after a profile creation if you chose a gender by mistake. Otherwise they advise you to create a new profile.
I guess changing gender of a user who already bought stuff (clothes, poses) could be problematic. And if you were to lose all you already bought, it would be easier to create a new profile with the new gender anyway.
But follow Zuzannah's advice and ask Support, maybe their policy as changed on this subject