[null and void]

In those days families did not move because a daughter was pregnant out-of-wedlock...

No. In those days the daughter would leave town for a vacation/job/health reasons, etc. and go to a home for unwed mothers to quietly have the kid and put him up for adoption.

[Gemsbok]

So how do you know if she had a kid between Junior and Senior Year over the summer in Hawaii?

With no valid BC, who knows the what , when, where, or how.

All we know is that the evidence is well buried.