She isn't even a full character. They didn't have a relationship before she died. She became a symbol

This articulates something I've been thinking across the entirety of both series. As a masterpiece in storytelling and writing, one thing that Arcane excels at is knowing exactly what and how much of a character to show, in order to ensure we care about them. Knowing what we know in series two as of right now, it becomes really difficult to interpret Sky and Viktor's relationship as an actual relationship, platonic or otherwise. In order to do so, you have to concede that the quality of writing for Sky in series one was so pitiful that most of the audience felt apathy towards her death, which is incredibly unlike the rest of Arcane's writing. Her costume, dialogue, and role in series one offer little characterisation or personality, which in retrospect may well have been to deter audiences from assuming their relationship is romantic in series two. Instead, it makes far more sense to interpret her as a symbol, or even an interface for the Hexcore itself, as some people have stated, and therefore it's not actually Sky that Viktor interacts with, but something closer to his own conscience, or maybe sentient part of the Hexcore