"erstwhile wife" is a correct and usable phrase in written English.
It is often used to refer to someone's former spouse or former partner. Example: After their divorce, Jack referred to his erstwhile wife as his "ex-wife" but still maintained a friendly relationship with her for the sake of their children.
The then-32-year-old and his erstwhile pop-star wife Victoria were among the world's most recognisable faces.
After Beryl died, some of the erstwhile young diplomatic wives from different Smedley missions testified to their luck that Beryl was not, as one of them put it, a "dreaded diplomatic queen bee".
When Saint Phalle entered the asylum, in the early nineteen-fifties, she was a twenty-two-year-old wife, mother, erstwhile fashion model, and lapsed French aristocrat.
After all, the case centered on the leak of a surreptitiously videotaped sexual encounter between Hogan, the professional wrestler, and the wife of his erstwhile best friend, who is named Bubba the Love Sponge.
Mr. West, for his part, offers up the verbal bravura afresh on a day of reckoning that results in face-offs with his estranged wife (Amanda Drew, excellent), erstwhile lover (the sweet-faced Martin Hutson), and Byron-fixated colleague (a beaky Penny Downie, in the only strained performance of the night).
The internet and television are awash with the story that Hollywood A-list celebrity, erstwhile Darling Bud of May and wife of Michael Douglas, Catherine Zeta-Jones, sought help with mental-health condition bipolar II disorder earlier this month.
Betrayals are made, loyalties shift and Antony finally springs into action...not to battle but to marry Caesar's sister Octavia (Charise Castro Smith) after his wife dies, placating his erstwhile partner in the process.
The combat was decreed in 1386 to contest charges of rape Carrouges had brought against his neighbour and erstwhile friend Jacques Le Gris on behalf of his wife Marguerite.
In the bunker with Mr. Gbagbo were his wife, children, grandchildren and ministers in his erstwhile government, Mr. Achi said.
