I'm currently thinking that Mirys had already been living in the Middle Ward before things ended up happening with her parents disappearing and all that, since being there already would mean it wasn't a long commute for her father going to/from work, but Mirys herself actually going out anywhere was somewhat rare because she would want/need to do something to hide the hair and ears and doing that whenever she wanted to go out was really just Annoying.

So for that first year of being at the NSO, Mirys would have been familiar with some places already but not too much else, and definitely could have used a guide if you want to go with Yang having filled that role. It'd give her a head start toward being someone that Mirys is actually willing to trust, especially if there'd been an effort to not go making her uncomfortable.