-Have her wear some outlandish nail polish colour.
-Have her wear clothes that are completely inappropriate for the weather, skimpy if it's cold outside, huge sweaters etc if it is hot.
-Have her wear childish jewellery; pink plastic rings etc, and/or take lunch to work in a childish lunchbox and carry a pubescent girl's style of purse or bag
-Have her decorate her cubicle (if allowed) with embarrassing posters
-Have her put itching powder in her bra, panties, pantyhose at the beginning of the working day