@evitodeus liked for a starter!
So... what’s so unnerving about Gilles de Rais’ Caster form, anyway? Is it the eyes or something? For her, the Caster’s eyes are funny, looking, but alas, in terms of having conversations with other Servants, there’s no exception. Yet.
And yes, it can be a hunch, but the spellbook he has with him sure evoke a sense of familiarity. Mainly because she’s an avatar of an Outer God. But that, she won’t let bother her that much.
Either way, she would approach the Caster in black coat, looking up to him, and would say “Hi there.” in order to hopefully get his attention.
Surely, she was right to not judge by appearance alone and give the benefit of the doubt in terms of approaching Gilles de Rais as a Caster. Right?