Understanding 'Ephemeral' in Context

In a contemporary novel, the protagonist reflects on a critical moment in her life, recalling the day her childhood home was sold.

As she stands at the edge of the property, memories flood her mind, filled with both nostalgia and a pang of loss. She recognizes the ephemeral nature of life, realizing that every cherished moment is temporarily encapsulated in time. This realization spurs her to embrace the transient beauty of each experience.

Which of the following words most closely matches the meaning of ephemeral as used in the passage?