Katherine's sharp gaze flicks from Stefan to Elena - her glare intensifying a little as it settles on her doppelgänger - and back to Stefan again.

"I don't know, Stefan, you two sure looked cozy together," she retorts, a sarcastic emphasis on the word. "Oh, won't it, now? Again, how very convenient."

In the back of her mind Katherine knows she's being unfair and unreasonable, aware that if Stefan can't break the thin chain connecting him and Elena with his supernatural strength, then doubtless nothing could. But at the moment, she just doesn't care.