The soon-to-be bride (her wedding to investment banker Marc Mezvinsky is slated for Saturday in Rhinebeck) was wearing her hair in a formal updo and full makeup, reports WWD - likely a dress rehearsal for the big day.
Hillary Rodham Clinton, who was multi-tasking as Secretary of State and mother-of-the-bride, had arrived 15 minutes earlier, each woman accompanied by a posse of Secret Service types, the publication reported.
Though Wang has declined to comment, it is rumored that she will also design the bridesmaids' dresses and even the flower girls' frocks.
Don't count Hilary-fave Oscar de la Renta out of the first daughter fashion-mix, though a spokeswoman there wouldn't confirm.
Both Chelsea and her mom have been spotted at the designer's Seventh Avenue showroom during recent months. And mama, according to WWD, was seen dashing into the place earlier Wednesday.