Answer:
The Proust effect.
Explanation:
This is a type of medical explanation for the very strong recollection of memory after being triggered by sensory simulators. The fact that Brad and Angie fell in love created memories within her mind. The one thing that linked Angie to Brads thoughts was his golden retriever, there are strong emotional bonds with the sight, smell and touch.
Seeing the labrador retriever re-triggered those memories and therefore making the Proust effect come into play.