Standing in the toy store, holly spotted a vintage barbie and had a memory of playing with her best friend in her basement. the was so true-to-life, she thought she was eight years old again. foreshadow flashback plot soliloquy

Foreshadow: be a warning or indication of (a future event)
Flashback: a scene in a movie, novel, etc., set in a time earlier than the main story.
Plot: the main events of a play, novel, movie, or similar work, devised and presented by the writer as an interrelated sequence.
Soliloquy: an act of speaking one's thoughts aloud when by oneself or regardless of any hearers, especially by a character in a play.
So in this case, the correct answer is flashback.