Hi, not entirely sure what you're asking here but I'll give it a shot.
This is indeed an example of personification. "The flower of the day," an object which lacks human sentience and features, is poetically described here as taking actions typically taken by humans. Flowers don't usually sigh or sit down; humans do this. This is why this is an example of personification – since the flower is the one who is supposedly taking these humanoid actions.
