She earlier said she had precisely three articles of clothing on. We can clearly see Shirt, Bra, and Skirt. Which means there's nothing else under said skirt, hence the conveniently located modesty shadow.
I rather doubt they'll be getting off the sofa for a while, although they may test the structural integrity of the sofa. Vigorously. After all, vigorous testing of safety standards is an important part of engineering. Right?