GEN Alum was single for a year after he graduated as I had another year left in college. He roomed with 2 other butterbar classmates who also were engaged to college seniors. Both roomies had fiancees in other states and ended up getting "secretly" married in civil ceremonies as well as church ceremonies later on. AFAIK, the parents and families never knew. For one spouse, it was a good thing they had the earlier date as a legality as the guy ended up having a midlife affair just over his 20-year mark and leaving her and the 3 kids.
She was eligible for the benefits under the 20-20-20 rule as opposed to only being married 19 years of the active-duty years so she wasn't left quite as high and dry. It didn't help her completely but it was better than nothing.