Cassian simply saw Sky as another employee of HexTech. A friend may be a stretch, but a well accounted associate, definitely.

If it wasn't for Viktor's estranged past with the young scholar, admittedly, Cassian would've have talked to her as much as he had, which already wasn't much. She was kind though, he could admit. Perhaps if he had the time, they could've been more well acquainted with one another.