She's not sure she totally gets the meaning behind the question, but Root does her best to answer honestly. With Shaw, she's abandoned trying to manipulate her long ago, certainly since her disappearance. She just treasures her being in her arms at all. Whether they're fighting or snuggling, she's just glad she's there.

"I've always been weird," she confesses. "And I'm still not convinced I'm not dead. Which is annoying, honestly, because I don't believe in the afterlife."

Logically, she should be dead, and this should be the afterlife. But there's nothing logical about life after death at all, so Root is being forced to question every basic tenant of reality as it is. Probably similar to what Shaw's going through with questioning whether this is a simulation.

"But so long as you're here, I won't take the chance that you're not real. Not my Sameen."

Her arms squeeze tightly around her, bracing, enough to suffocate. She couldn't live with believing the alternative, and betting wrong. Thinking Shaw was real -- real being a sentient, separate consciousness, an independent entity with a continuity to who Root had fallen for -- and being mistaken... that she could live with.