[Clare:] I regard my likeness and she returns my gaze. I place my finger on her forehead and say, "Vanish," but it is she who will stay; I am the one who is vanishing. (3.4.6)
After Henry's death, Clare draws an image of herself to assert her existence in this life, to create an identity that lasts. She knows that it's her drawing – this physical evidence – that will live on when she passes away.