It sounds genuine to me.
It would be extremely unlikely to me that someone who happened to live in the same area that the winning ticket was sold would happen to have an old ticket where she'd chosen exactly the same six numbers (and could then simply remove the date, etc).
To forge such a ticket would probably take skills well beyond those of most people and, even if they could do so, they still wouldn't know exactly where the winning ticket had been sold (as Camelot only reveal the general area).