Definately brown leghorn she looks just like the 5 I have and mine are CRAZY!! They love to buzz the other birds when they are out in the run and drive them bonkers!
Sweet birds but kinda flighty at least mine are. I am trying to withhod final judgement on them until I see how they are going to be as layers. Mine are approaching 18 weeks also.
If the other birds let them live long enough to begin laying!!! BG my RIR roo is beginning to get a very "I'm king of this forest" type tude with them everytime they buzz him.