as for why..your guess is as good as mine..but that behaviour is not unheard of.
sometimes they take their dominant role too seriously and start behaving like cockerels and even physically change too look like one. But even if it would go that far..they never will be able to fertilize any eggs.
If you have mirror..try her...by putting it in the pen and see if she is aiming to attack the 'other one'. If she is trying to do the cockerel role she will try to do cockerel fight with the mirror...or if she is clever than that she don't ::) ;D
Keep eye on her..if she still keep laying eggs..nothing to worry..unless she is too rough with others (there is few tricks for that too..but only if she is being nuisance)
But if she doing the cockerel thing..she propably stops laying....then is up to you what you decide to do.. :-\
So at the moment..keep eye on what happens and if her behaviour is disturbing others...there is not need for worry... ;)
