Witches of Wherewithal by Alexandra Sharp

Witches once sought refuge atop Wherewithal Island’s icy, mile-high cliffs, escaping the hangman’s gallows spreading from Salem to beyond. But by 1947 Theodora Ashe is the only witch left.
At least she was until her powers disappeared the same time as her husband did, with sheets still warm from their wedding night.
But good riddance to bad magic. Witchcraft only ever brought Theodora scandal and heartbreak, so if no longer being a witch means finally getting some peace, she’s happy to become a footnote to history.
Until someone starts targeting her childhood love, the charming and politically ascendant John Dove, and trying to pin the would-be murder on Theodora. To clear her name and save John, she must re-enter a world of high society dinners, tabloid headlines, realpolitik, and a struggle for power in the vacuum where witches once held sway – and play the part of the witch she used to be.
As assassination attempts escalate and the body count rises, Theodora’s abilities begin to reemerge in tandem with her feelings for John. She begins to uncover the raw power she might wield as the last witch not just on Wherewithal, but in the world, and the lengths someone might go to make sure she never gets the chance.