What I meant about Tanya and Nika was that even after she put on the meteor core, they remembered Suou and had actual memories with her before she put it on, ie the confession, the feelings between Tanya and Nika, how Tanya wasn't a contractor before, etc.

Knowing them, if they had an explanation it'd probably be something like there's a 2 year limit on how long her memories can retain until she needs the meteor core or something. Since she apparently was created 2 years ago.