Lydia is Scott’s Emissary! Also why Lydia is immune!
Spoilers for 3×09 ‘The Girl Who Knew Too Much’ said that there would be a scene which cements the bond between Scott and Lydia which involves how she could help Scott’s pack in the future, and after learning of Deaton and Morrell’s roles in their respective packs, Lydia could be what Deaton was to the Hale pack for Scott.
What was that you say – Lydia isn’t a druid? Well, according to sources, there are some people who are destined to become shaman Druid and they answer ‘The Calling.’ The Calling usually happens after an initiatory physical illness – and Lydia went through exactly that after being attacked by Peter at the end of season one. Lydia surviving the attack makes her known as a ‘Wounded Healer’ as she had the ability to heal herself or be healed by spirits.
Lydia having underlying shamanistic powers would explain why she is immune; if it is an emissary’s duty to keep the werewolf pack’s humanity, then of course they’d need to remain human. As well as this, it would also explain how she was able to see the Darach in the fire as well as heard the replays of the guest suicides in 3×06 ‘Motel California’ – she’s probably crossed to the other world before so therefore still has a link to it.
Lydia being linked to Scott’s pack could explain why Scott knew it was Lydia’s scream in 2×01 ‘Omega’ and why Scott reacted the way he did when he say that Aiden was making moves on Lydia in 3×05 ‘Unleashed’. Scott subconsciously felt a pull and protectiveness to Lydia which shows the relationship between an alpha and their emissary.
This links in with this post about Lydia being a ‘psychopomp.’
(I’m still researching this, but I wanted to get this out before the episode :D)