I can't for the life of me identify the 1st panel character. The artist doesn't tag her in his pixiv "C83 sample" post either. He identifies Marseille, Raisa, and Matsumiya Aya who appears in an unrelated picture of the post stack.
The artist also didn't use the "original character" or "original witch" tag.
Edit:I plan on buying the comic when I can, if all else fails I'll identify her then.