ponko was "particular" even before the death of chiaki (we see the flashback), she simply understand her desire. The true last mystery was the war and the fact that ponko was a combat robot, something in the war make her what she is...
I get the point, but to me, that not seems neither a child, that was a eggs fertilized by the villain implanted in the FMC, more like Alien case that a conception, we don't know neither if the unborn was human-like or animal-like. why that would count as the tenth child? Plus in the prophecy was...