He doesn't know what to say to that, how to respond. He hasn't entirely figured this place out yet, hasn't figured out if it's some kind of purgatory or prolonged hallucination, or something else entirely. But he knows there's truth in her words.
Allison is alive. And if she's alive, it means the ritual works at some point in the future. It means that Stiles isn't.
In a sense, she's right. Somehow the relief he thought he'd feel doesn't come. He shuts his eyes for a moment, reaching out and resting a hand against the wall. "Yeah. Not yet for me, but...yeah." He's not sure it's something he can change if they get sent back home. He's not sure it's something he would. Scott begged him not to go through with the ritual, but he knows how much Scott loves Allison. How can he be the one thing that keeps his best friend from having a happily ever after? How is that fair?