I don't know if you could call it evolution. It very well may be a mutation, but apparently there were serious problems with her kidney functions, so it may not be a "good" mutation. Also, very young children are still developing rapidly, and it may just be that whatever genetic switch triggers such things hadn't yet turned off, allowing new kidneys to be developed when the old ones failed.

Another thing to consider is that the new organs have the same rare structure as the old ones, so I would be concerned about problems down the line, but now that the docs are aware of the problems they can monitor her much more closely. Either way, I wouldn't classify it as a miracle. A happy story, yes, and strange for sure, but no miracle.

On the other hand, maybe she's part Klingon, with duplicate organs!