I don't see any "sickles" hanging down by the tail, the comb is quite small and her tail isn't shaped like a boys.
As to the breed, I'd guess it's a at least half Rock, due to it's yellow feet. The other breed it's mixed with might be a Dark Brahma or some other silver laced breed.
Very pretty girl, she'll be a lovely addition or is that addiction to your flock!
First I vote girl, 2nd she looks just like one that I hatched out from my barnyard mixes. My chick was yellow down with some black spots on her back and a black line on her head her wing and tail feathers show the same barring as your girl. My rooster is a Cochin mix (Cochin/white Plymouth rock white bantams) his girls are red sex link, BO, BR, Austrolorp (sp) now my rooster looks funny he is barred on the top but his chest area is laced so I was thinking that she might be from a red sex link and him or maybe a BO cross. whatever she is she is pretty.