How does Catherine feel about Gatsby and Myrtle's affair?

I'm sorry, Gatsby and Myrtle did not have an affair. In Chapter Eight, the only mention of Catherine is as follows;

They had difficulty in locating the sister, Catherine. She must have broken her rule against drinking that night, for when she arrived she was stupid with liquor and unable to understand that the ambulance had already gone to Flushing. When they convinced her of this, she immediately fainted, as if that was the intolerable part of the affair. Some one, kind or curious, took her in his car and drove her in the wake of her sister’s body.