6/2/angels don't need no last roll
They both know what this means. Picking up a few basic first aid tricks is not the same thing as being a qualified doctor, and even if Anna were she probably couldn't do anything for him anyway. Probably presumed dead, they're cut off from the rest of the group and no one is going to come looking for them. That's always been a rule, one Anna's had to force herself to stick to no matter how hard it's been. The survivors are smart, that's why they're survivors. They'll be okay.
There's more pressing issues at hand anyway, like the rather serious wound Cas is nursing that she can't do anything about. As an angel trapped as a human and cut off from Heaven, feeling comparatively useless is nothing new. This is something else entirely though, she can't do anything about this and all Anna has left is to make it as easy as possible.
So she smiles. She forces on a smile that isn't even close to looking genuine, and she touches his shoulder gently as she pointedly averts her eyes away from the bleeding, focusing instead on her own hand and the point it comes into contact with his arm. It's warm. She can't help but think: not for much longer.
"Never would have guessed it would happen like this."