100% hen. I don't see any hackle or saddle feathers on her. Her much would be much bigger/brighter at her age and would have brighter coloring. And yes hens Can get sickle feathers like that. I have about 14 with sickle feathers and all are great layers. I'm not sure why you think rooster. I don't see any signs of cockerel
I say pullet too because that comb is small and not red enough to be a boy at four months, plus those sickle feathers are not actually pointed. They are rounded, the same as the hackle feathers.