A smack to your head wouldn't satisfy Diana. She poured her heart and tears out over your death, praying to the gods and whatever she believes in to just give you another chance to live. Then you just somehow wake up from the death itself and with the most nonchalant say that yeah, you are immortal. When you got your powers, you did tell her about how they work, but you somehow 'forgot' to tell your adopted mother that it includes immortality as well, and she doesn't need to panic over you dying. Oh, Diana would pinch- or punch you, if she weren't feeling so much. "You... idiot child." At the end, she decides to pull you into a crushing embrace. After all, that's what she wanted, a miracle.