Her* wings!

Casey is all girl!
Strudel, you just need to take pictures of your entire flock and share em! =D
As far as the orange cheek patch? Males and females have them! The only time that they "don't" have them, is when they are of the blue mutation (aka whiteface). The blue mutation removes reds, oranges, yellows and pinks. In green based birds, you end up with a blue bird. In a grey based bird, you end up with, well, a grey and white bird! In white based birds, you end up with white birds! (think, a sulphur crested cockatoo that's completely white)
Both of my pied hens have laid eggs, so there's no doubt that they are hens! Of course, I didn't need them to lay eggs to know this fact. Although one whistles, neither talks, sings or does heart wings.
The male whiteface I had paired up with a lutino pearl hen and they produced various colored offspring! He didn't talk either, nor whistled, but he had a gorgeous song and he did do heart wings.
Susanne Russo has a great article on sexing cockatiels
Sexing Cockatiels - Just Cockatiels!
And she has comparison photos of a whiteface male vs whiteface hen.
Whiteface - Just Cockatiels!
If the bird is not a pearl, pied, ino, or a few other face altering mutations, then you can visually sex most mutations via the amount of grey in the face. Don't even pay attention as to whether or not they have the orange cheek patch! It doesn't matter! Not when it comes to sexing! Adult males have a clear face (i.e. no grey) and females have grey faces.
And of course you can also sex via flights, tails, rump and behavior.