I (sadly) have to agree.

Summer romances end, just like most high school romances of that time (usually due to the draft).
Tight knit special circumstances like that make for seemingly increased time, but then it has to end.

As a male, I had a couple of those romances and actually met one of the young ladies later in life (after marriage).
Laughs about how innocent time was then (early Viet Nam Era) and "how are yous".