Taylor Swift’s discography is full of references to real people, but what happens when one of those people is your relative?

Frances Osborne recently found out when her great-grandmother Idina Sackville seemingly became the inspiration for “The Bolter” from Swift’s 11th album, The Tortured Poets Department, which dropped on April 19. Swift, 34, announced “The Bolter” variant of the album in February, but it was weeks before Osborne realized her possible connection to the song.

“Somebody may have mentioned something to me around mid-February,” Osborne exclusively told noting that she’d been in a “quiet zone” while working on her next book. “I wasn’t that tuned into the outside world.”

On April 20, however, everything changed. “I was riveted,” Osborne said.

Osborne is the author of several books including The Bolter, which debuted in 2008. Sackville, who died in 1955 at age 62, was one of Osborne’s great-grandmothers on her mother’s side. She earned the nickname “The Bolter” because of her reputation for fleeing her marriages.

Swift’s song doesn’t mention Sackville by name, but the similarities are there if you know where to look, and Osborne certainly does.

“Idina was this figure of extraordinary glamour, but she was both a figure of wonder and a black sheep at the same time,” she explained to Us. “She was criticized and she was all over the headlines everywhere. People wrote bad things about her because what did she do? She behaved independently and behaved as a man did, and the arrows rained down.”

Sackville, who was also a cousin of the writer and garden designer Vita Sackville-West, chiefly made headlines because of her love life — she was married and divorced five times before her death. Perhaps most famously, she left her first husband, Euan Wallace, and their two sons, but as Osborne notes in her book, both Sackville and Wallace were unfaithful to each other during that period. Later, Sackville and her third husband, Josslyn Hay, agreed to an open marriage, but only one of them was saddled with a disparaging nickname.

“It’s a derogatory term, implying that a woman who leaves a man has something wrong with her — not that the relationship or the man might be inappropriate or harmful. Whereas a man who leaves a woman is a man,” Osborne said, emphasizing that the word “bolter” traditionally refers to a horse that has run away. “As Swift makes clear in her song, there’s always something that makes that horse run. And when [the term] was first used, it was very belittling.”

She went on to note that cursory readings of Swift’s “The Bolter” have talked about the song’s narrator having commitment issues, but Osborne doesn’t see it that way at all. Like Sackville, Swift’s heroine is leaving relationships because they’re not right for her — not because she’s afraid of tying herself down.

“Idina’s social crime at the time was to keep on marrying her boyfriends,” Osborne explained. “[She thought], ‘This is it, this is true love.’ And then the crashing disappointment, which again, we see in the song. And, you know, every breakup was different.”

Whether you read “The Bolter” lyrics as purely autobiographical, there’s no question that Sackville and Swift share a predilection for romanticism. And like Sackville, Swift has a big reputation that precedes her whenever she meets new people.