this isn't an original theory, but what if vespera was a vacker?

she had worked with luzia vacker before, and we know the vackers are a prestigious family who wouldn't work with just anyone. and even if it was for council purposes, luzia would have had a right to choose who to work with and she chose vespera.

and when sophie first described vespera's voice in nightfall, it was said that vespera had a crisp accent, like all the other vackers.

although she doesn't have teal eyes, della doesn't either. she could have married into the family [ unlikely ] or had a mother or father who didn't have teal eyes and that trait passed down to her.

and you have to admit, vespera vacker sounds pretty interesting