1905 Macy's White Wear for Ladies, Misses and Children: Corset covers, ladies french corset-cover and open drawers in one, ladies chemise or corset-cover and underskirt in one, ladies circular petticoat-skirt .
I think she has just unfastened her bodice. Corset (no cover) tied at back. Petticoat (or drawers, i guess) must be held low in front by the corset hook. Chemise under the corset. Is this a strip-tease?