JC Penney has this cool faux-fur vest for that can be incorporated into many kids Halloween costume ideas. I can’t tell from the pic, but I am assuming the belt is removable if desired. They are not usually secured.
For a TRADITIONAL GIRL OWL: Wear a brown/black/cream/white long sleeve shirt (your choice) underneath the vest and add a brown skirt, tights, and leg warmers. You could use a khaki school uniform jumper or a brown skirt with a print on it works really well.
Even cuter for girls would be