Instinct almost has October reaching over to touch him, to offer him physical comfort somehow, but she stops herself before she actually moves. She likes Alex well enough based on what little she knows about him, but she doesn't want to push things, especially since she has no idea how he'd even react to that.

So, when in doubt, default to joking to attempt to lighten the mood.

"Are you sure it's the mask doing that? Because you've seen that kind of shit before and didn't think anything of it."

...okay, maybe that joke sucks and is only "funny" to her in a very morbid way because she knows she's dead. And, unless she forgot about telling him, Alex doesn't. (At the very least, joking about her death might distract him from the mask stuff for a moment or two.)