When I took the roo from my rir flock for about 4 months then let some cockerels out to free range with the ladies in the coop my head hen started acting like a roo. She'd put her 'hackles' up, peck and fight the cockerels through the fence! Still layed an egg every day but won her little...
Looks like a rhode island red or new hampshire red pullet. Females have been known to take on the roo role if none are present. Rhode island red girls I had were a bit darker red but the body of yours looks like a female.