I think you're just caught in a situation where you were wrong in your initial post and unwilling to admit it. It's ok, that's hard to do sometimes.

If Kratos' outfit in Fortnite was different from his GoW outfit, and someone cosplayed as the Fortnite version and said "My Kratos (Fortnite) cosplay", then that situation is comparable. If his Fortnite skin was identical to his GoW skin, and her Arcane skin was identical to her LoL skin, you might have a point.

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But her Arcane skin is different from her LoL skin and the outfit is clearly cosplaying the Arcane version. So you don't.