The main thing is the small comb and wattles, with not too much color. She looks almost mature in size, and a male would show a larger, more colorful comb and wattles at that age.
That is the simplest way to tell.
She also lacks male specific feathering. That mainly shows in long, very slim...
They fit fairly well for Brahmas in shape, but I suspect they might be crossed with white Langshans because the rooster in particular shows that body type. The length of the body seems a little short to me, and the male's tail is carried higher than the standard.
Also, the females appear to...
3 Legbar
5 must be your Polish
8 is the olive egger, probably
9 Cookies and Cream
7 and 4 could be blue birchen Marans
10 probably the Swedish Flower hen
11 Chocolate Orpington
6 black Ameraucana
Some people just aren't interested in learning. That's fine but when you are selling something it helps to have information to give to customers. You make more money that way.
Demasiado pronto. Plumas de pechos de los gallitos sera negros. Plumas de pechos de las pollitas sera perdiz platas.
No hablo mucho Espanol pero lo intente.
It's just too early, in my opinion. The comb is pale, so that's good, but nothing else really stands out. If you need to know soon, you could send a feather sample to a lab and they will tell you the gender with accuracy, but for a price.
It has no male specific feathering. The saddle feathers are frayed. I think it is female, but I would give it some more time in case it is a late developer.
These are mixes. I think buff Orpington is one parent of all of them.
The one in the second picture probably has something like Leghorn as the other parent.
The one in the third picture probably has Easter egger as the other parent.
There was a separate picture with a different bird that is now gone.
The rooster in the original post has a crest, so it can't be a pure Wyandotte of any variety.