My Rhode Island Reds developed in a similar way to this one with the really long neck and slopping body style like yours...made me wonder alittle too, but, thankfully, they are all long-necked pullets!!
When my Barred Rocks were about 4 or 5 months the one that turned out to be my roo (well the color shoudl have given him away but I was too chicken ignorant to realize that) got a huge comb and wattles so much quicker than my pullets that I think your chicken would be showing those too if it were a roo as big as it is now. Coming from a true beginner here, I would go with the barn boots and say she is very pretty pullet!