This dress would look great with her red hair. The back cut-out is a nice call back to her friendship with Margaery.
This Oscar de la Renta dress has princess-y elements but it is much more mature with a patchwork lace bodice.
J. Mendel gown. This is the perfect dress to wear as a master manipulator. I'm sure she's picked up some skills from her time with Littlefinger.
Monique Lhuillier dress is a little sweet but it's still very glamorous.
in this with a feather cape.