There are three more window sills, if I block that one. (We have four large windows that are all open now due to the heat - high of 89 today). -thinking on it, though.
Again just thinking out loud here, What about attaching hardware cloth to a frame that's big enough to cover the window and sills, then hinge it on the windows so you can lift it to have access to opening and closing the windows and the hardware cloth would not block out the airflow? Don't know if this will stop her from crowing or not. Just trying to help.