Originally Posted by
Mrs Spratt:
“Erm - if Amy's parents never existed how did Amy exist?
”
Same with everything in the crack.
The Weeping Angels in Flesh and Stone/Time of the Angels never existed yet River was still freed, sent after the Byzantium, and then freed after for her work.
Rory never existed yet the ring still existed.
The ducks in Leadworth never existed but the pond did.
Her parents never existed yet she still did.
The cracks erase you from existance, and from memories, but not from the effects of what they did. Hence the ring, the photo of Rory, Amy, River Song despite post 2010 Earth not existing etc etc.
As they said, Amy was the girl who didn't make sense, having no parents but still existing etc. Yet deep down she still remembered parts of them, such as the fact that her mum used to put the faces in the apples. Erasing from time because of the cracks isn't the same as if you'd been killed as a baby. Its like removing someone from a photo with Photoshop. The person isn't there, and someone in the photo may not know who has been removed, but there are still signs. An arm that was raised to go around their shoulder, still there but around no-one. A gap between people standing in a group etc. The person was never there but their affects remain.