If she lives according to the mores of the day, then she is relatively chaste and disease-free compared to the promiscuous sluts that infest our society.
I find that very attractive.
I’m not sure your views of morality in 1940s is supported by the historical record. Anecdotally, remember Ike and Kay.
Or, if you prefer hard numbers, check out Paragraph 13 here:
http://www.nisra.gov.uk/archive/demography/publications/annual_reports/historical/1944.pdf
from 1944. “The number of illegitimate births and the proportion to the total births are the highest on record”
Those Americans waiting for D-Day had to do something with their time, and the English guys had been off at war almost 5 years by then.