Enchantress, known as Spellbinder in North America, is the third Night World book and tells the story of Thea Harman, a Circle Twilight witch who finds her soulmate - a human. Towards the end of the book, Thea is forced to leave the Night World after betraying it's secrets. Before she leaves, Aradia the Witch Maiden, advises her to seek out the newly reformed Circle Daybreak. She is also responsible for the reference to Ash:
started going peculiar. I've even heard that
they're talking about finding human soulmates,
just like you. You might try and contact
them and see what the story is." (page 224)
OK, so it's not a direct reference, but the subject is unmistakable. Aradia is clearly talking about Ash and Mary-Lynnette, and possibly Poppy and James. So, is it true that Ash has gone "peculiar"? By Night World standards, that's certainly what it must seem like.