She seems... frightened? Of him? Walter doesn't quite understand. She's otherworldly and beyond all this bullshit and he's just a sad lump of meat, what does she have to fear from him?

The death rattle croak is enough to startle him, but not alarm. It's just a noise. He's heard worse ones. What does surprise him is the talking.

"You're real." Walter's voice is quiet, maybe a tad bit reverent. He stretches out a hand towards her once he's close enough. His fingers light brush past some of that long hair, and lightly touch very very cold skin. As if the question of her tangibility had any kind of meaning.

Don't ask him why, though.