It's impossible to tell at this age without DNA. I'm just going by how my girls look with head shape & the head is not as broad as male's I have. Of course, seeing as how Joey is a mutation and would be multiple generations removed from original Australian stock, she is rather small so this can always impact on visual sexing. If you want to be 100% sure I'd suggest either taking to an avian vet for surgical sexing or sending feathers away for DNA - if you care either way. It would be better for you (genetically) if you wanted to breed if Joey is a boy - so I'd like to be proved wrong - which at this age I may well be (I'm no expert - just own a few).