(SPOILER)Well, the most obvious proof that this is not Shelke is that Shelke was taken from Shalua ten years ago. That's kind of why Shalua's been looking for her for ten years. I was under the impression that she was in Deepground all that time. She certainly had to have been in Deepground under Midgar for the past three years, because Reeve explicitly states that President Shinra, Heidegger, and Scarlett would have known about it. And considering all of them died three years previous to Dirge of Cerberus, Shelke must have been a member of Deepground for at least that long, most likely longer, considering she's a member of the Tsviets.