The answer to that question is incorrect. Yukari's character is Yuyuko Saigyouji, who's one of her closest friends and rivals. Remilia Scarlet is a well-known vampire, and the head of the Scarlet Devil Mansion, who first appeared in'Touhou 6: Embodiment of the Scarlet Devil'.
Voicing Success: A Melodic Journey Through Yukari Tamura's Anime Universe