I was planning on misleading you as long as possible, but lkasjf no, they're just shitheads at one another. She pushes and he pushes back harder and neither learns a lesson. It is a very (un)fruitful relationship.

Quistis is p chill, just awkward to the point of being painful sometimes. She'll be glad to meet him, regardless! She looks at Nagisa like he's a kid and she's an adult, but she's only nineteen (she doesn't really tell anyone this, however, so everyone kind of just assumes she's 25 or something).