Perhaps... but that would be most perverse of the magic... perhaps it took it that I'd addressed more than two persons (Miss Brown, Miss Longbottom, and Gryffindor's Prefects in general?), but if that's the case, it took two at random.
In that case, I expect Miss Brown is unable to see the message.
Private Message to Mr Finnigan
In that case, I expect Miss Brown is unable to see the message.