Sigewinne is playable Hydro character in Genshin Impact, released in Version 4.7. As the head nurse of the Fortress of Meropide infirmary, she's a Melusine with a unique physique closer to that of a human due to drinking a potion that changed her into her current form.
Her name is pronounced "SEEZJ-ween" (roughly, like the words "siege" and "wean").