Nyx Goddes of night and the daughter of Twilight in crossover between Witcher and "Past Sins" MLP-fanfiction. https://www.fimfiction.net/story/41596/past-sins I guess some people who really care about MLP still remember it. OK she is not goddes she's just immortal alicorn foal created in interrapted magical ritual which should reborn Nightmare Moon and adopted by Twilight who has found her.
The idea appeared during Witcher 3 walk-through. All these NPCs with their comments about cat eyes. X) I thougt even add PS to her advertisment "I DON'T catch mice!" (I played Russian version so I suppose there may be some differences in localizations) and the ending of "Past Sins" where she defeats more monsters than Geralt could see in 10 years. And those who played or watched "Blood and Wine" DLC should remember the funniest quest in the game "What horses talk about".
I see some more similarites between her and witchers so she fits perfectly but you can find out by yourself.