Board Thread:Theories Discussion/@comment-13376834-20130430230244/@comment-6192846-20150810013339

We're told the demons themselves weren't actually made directly from Eve's magical power-infused body, which was the original impression mothy was trying to flip around on his readers through Elluka. Pierrot then confirms said six actual demons were the god kin who slipped in when H&G were creating the vessels of sin (possibly under Seth's suggestion/instigation).

The existence of the Original Sin and H&G splitting it into seven fragments and apparently dividing these up along with six demons + Eve's soul is unexplained, but I don't see anything to suggest the idea that, even if the Original Sin is simply magic (Eve's or otherwise), it was able to have or develop a consciousness of its own separate from the demons; sounds like it would defeat the purpose of H&G using the demons/Eve.

Of course, separating the original abilities of the kin versus their abilities as demons (if there's a difference) is difficult, but there's neither mention nor implication that the demons lost anything during the events of the SCP story imo.

To draw this back to the op, I don't think the Waiter as an awakened vessel would be some incarnation of the "sin". If the Rin character is her, it wouldn't match up with what we've seen with either the Demon of Pride or what it represents (at least when it comes to her apparent inner sadness and loss).