Before I went to the farm store for chicks last June I studied hatchery catalogs so that I'd know what the chicks of the breeds I wanted ought to look like.
Then I lucked out -- having not only chosen the right farm store but, by going on the day that the chicks arrived, I was there on the day...
I'm no expert, but she seems too slim-built to be a bantam Orpington -- not to mention the wrong color for a buff and the yellow legs.
Game cross, maybe?