When I was thinking of a real-life character to feature for Unusual Historicals’ “First Ladies” theme, Saint Cuthburga came to mind.
First lady is defined as the wife of a political leader or the first woman recognized for a particular accomplishment. In this case, Cuthburga is the ex-wife of a seventh-century Northumbrian king.
Usually, a divorce in the Dark Ages was an insult to the woman and her family, so it was not done lightly. When Charlemagne parted from his second wife in the eighth century, he ended up going to war with his former father-in-law. As for Himiltrude, the first ex-wife, the consequences of that separation are the subject of my work in progress, Queen of the Darkest Hour. (Whether Himiltrude was a concubine or a wife is a topic that deserves its own post.)
No one questions whether Cuthburga was a queen, although for how long is up for debate. Also the sister of a king, she founded Wimborne Minster at Dorset after she left her husband, and that decision would have an impact beyond her lifetime. Read my post about Cuthburga on Unusual Historicals.