The lady vanishes
Later in the movie (26:34) we can notice the use of dissolve to represent Iris’s fainting followed by a kaleidoscopic vision at 26:44. Later on, Iris looks at the passengers of her cabin and she seems to see Mrs. Froy’s face everywhere (48:05), to suggest the ‘hallucination’ Hitchcock blends the two images in superimposition.
Ultimately, the director uses a shot/reverse shot in the scene of Gilbert and Iris in the cabin restaurant (51:02), when the girl sees the name of the old lady written on the