I really do need to re-read that short story and remember what exactly happened with Mia and Ivy. I know she offered to be Ivy's blood source in exchange for feeding on Ivy's emotions (I think). But I can't remember all the other stuff.

I keep getting the ex-girlfriend Ivy doesn't want Rachel to meet vibe from the whole Mia situation, and I know that's not really how it was, but I think maybe there's a lot about Mia that Ivy doesn't want Rachel to know because true or not she sees a lot of herself in Mia.