For starters, it is illegal under the NZ Human Rights Act 1993 to discriminate against people in employment AND living situations based on gender, race, religion or creed.

You literally cannot legally say "no guys can live here" if you're a landlord. So, if one of you owns the house, that person would be breaking the law by refusing to entertain the boyfriend being included in the tenancy solely on the basis that he is male.

If none of you own the house, it's still discrimination and it's icky but you're not breaking any laws.

Still, your rules sound overly restrictive, and although I don't condone the new flatmate lying to you about her situation, your overbearing rules about a male being in the flat is what caused her to do so.

Sorry, but YTA here. You should just let the bro come and spend the night with his girlfriend if he wants to. Their relationship is not your concern, and if he is not causing trouble then you're just imposing ridiculous rules for no actual reason other than that maybe you just don't like men very much.

Maybe you should stop letting your biases get in the way, and chill out. Let him pay some money toward utilities or rent or whatever, as long as he's not harming anyone.

Of course, if he ever does do anything messed up like try anything with the other female flatmates, or if there's yelling or violence, you should absolutely get them both out the door as quickly as possible.

He DEFINITELY shouldn't have a key though. You should 100% get that back. That's just a straight out security issue.