Lydia takes the hug. Maybe it's because she just watched Jackson die or maybe it's because she feels like she's actually not alone, but she clings back and just shuts her eyes.

Then there's that moment where it sets in that she's hugging Stiles.

She lets go and pulls back. Distance.

"Dead? No. No! What are you talking about? I went to work and then Mordin wasn't there so I went to check on him. Then I woke up in someone's apartment--" Lydia halts her ramble and glares at him, "Stiles? How long was I gone?"