What is this chicken breed?

[SBFChickenGirl]

So basically her coloration just looks like a dark Brahma but she isn’t mixed with one.

Yes. It's a pretty common (but very striking) color on EE's. Of course, none of the pictures on the internet look exactly like your girl, but that's the fun thing about EEs. They are all unique!!!
Not my pic:

 

[Lacy Duckwing]

Is it possible she was mixed by a Americana and a dark brama

She very well could be. If she is, she got her looks and waddles from the Dark Brahma, and her egg color and legs from the Americana. One thing though, she has no feathers on her legs. I've bred feathered legged chickens with clean legged, and some of the chicks were clean legged whereas some weren't. I've bred Brahmas to a third generation and the feathers stayed. True, the second generation hen didn't have very much feathers.... but she still had them. I guess it's hard to figure out what breed(s) a chicken is- but it can be fun too. Either way, she's definitely an EE, just the waddles want to say she's not just a muffless one.

 

[Camilladavisss]

Yes. It's a pretty common (but very striking) color on EE's. Of course, none of the pictures on the internet look exactly like your girl, but that's the fun thing about EEs. They are all unique!!!
Not my pic:
View attachment 2447500

Ok thanks I don’t know much about the Easter egger bread but your info has been helpful

 

[TheOddOneOut]

I thought Easter eggers have fluffy cheeks. I know a Americana and Easter egger is kind of the same thing but I always thought they had fluffy cheeks?

Not the same thing.
EEs are mutts, Ameraucanas are pure. Easter Eggers have no standard at all, because they are mutts. https://www.backyardchickens.com/th...hink-you-have-an-ameraucana-do-check.1421663/