REGISTER TO REMOVE ADS
But then how can she have control over memories she doesn't even know?
Relation =\= ownership. Namine can look into Sora's Memories and rearrange them. She doesn't need her own Memories for that.
Think about it as you will of taking up someone else's diary or journal and messing around with it. Why would you need your own diary to be able to mess around with it?
This doesn't relate to Xion or Days all that much, but why is it that Roxas doesn't have Sora's memories? Is the time the person spends as a heartless the time during which memories flow into the nobody? I've never understood how this works >.<