PIC: Skinny Liberty Ross Wears Sexy Leather Pants to L.A. Concert

Rupert Sanders' estranged wife Liberty Ross stepped out Tuesday in L.A. wearing a big diamond ring -- on her middle finger.

The 33-year-old British model attended the Nokia Music launch concert for Janelle Monae at Club Nokia. Ross, who happily smiled for photographers on the carpet, looked skinny in a leather jacket and leather pants.

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Since Us Weekly broke the news that director Sanders, 41, had cheated with his Snow White and the Huntsman star, Kristen Stewart, 22, in mid-July, Ross hasn't been wearing her wedding ring.

On Tuesday, Ross still chose not to wear her ring, but she did accessorize her middle finger with a huge diamond rock.

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Sanders and Ross have two children together, Skyla, 7, and Tennyson, 5. Last week, the supermodel stepped out with her ex-boyfriend, Christopher Taylor, to attend The Serpentine Gallery party in London.

As revealed in the new issue of Us, on stands Friday, Stewart has recently reunited with her boyfriend, Robert Pattinson. Pattinson, 26, and his Twilight costar/girlfriend of three years have now moved back into together.

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As for Sanders and Ross' relationship? A source told Us late last month, "It's too early to tell what will happen with them."

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PIC: Skinny Liberty Ross Wears Sexy Leather Pants to L.A. Concert