PIC: Liberty Ross Walks Runway at Alexander Wang Show

Liberty Ross looked pretty good to begin with -- but looking flawless is an even better form of revenge!

On Saturday, nearly two months since she discovered that her director husband Rupert Sanders had cheated with his Snow White and the Huntsman star Kristen Stewart, the British model, 33, did what she does best: Work it!

PHOTOS: Kristen and Rupert's July 17 fling

Ross (who has graced the cover of British Vogue) was a surprise model on the runway at the Alexander Wang fashion show (sponsored by Fiji water) in NYC -- stunning the onlookers with her jet-black hair, and wearing a chic white look in an early snapshot taken by an attendee.

PHOTOS: Kristen and Rupert's road to infidelity

One of the onlookers? None other than Justin Theroux, Jennifer Aniston's hubby-to-be, who grinned and thanked well-wishers on his recent engagement.

PHOTOS: Women who've been cheated on

Together for ten years, Ross and Sanders, 41, share kids Skyla, 7, and Tennyson, 5. Their marital status? "It's too early to tell what will happen with them," a source recently told Us.

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PIC: Liberty Ross Walks Runway at Alexander Wang Show