To be fair, that only happened because she was weakened from both giving birth (which is incredibly long and painful if what I'm lead to believe is true), and having Kurama torn out of her (something that is supposed to kill a Jinchuriki instantly). Both those events happened within a few minutes of each other. The fact that she managed to not only maintain consciousness after suffering that literally fatal physical trauma but also restrain Kurama by herself with her chakra chains, and still hang on for a few minutes after being f%*king impaled, is proof that Kushina probably is not exaggerating in this fanart.