St. Vincent insists she and Cara Delevingne will be friends "always and forever".
The 35-year-old musician dated the supermodel for around 18 months until they split in September 2016, but they remain close and the 'New York' hitmaker - whose real name is Annie Clark - couldn't have made her new album, 'Masseduction', without having had the 'Paper Towns' star in her life.
Speaking to the new issue of Grazia magazine, she said: "[We'll be friends] always and forever. I definitely credit being around her for that expansion in my chest. This is me at my most literal. It's always been me, but the code was a little harder to crack. I was less comfortable being deeply sincere."
And St. Vincent doesn't understand why people are so fascinated about whether or not her songs are about Cara, or her other high-profile former lover, Kristen Stewart.
She said: "This is just me ... I've never wondered who Tom Waits was singing about on 'Big Black Mariah'. I've never wondered who Leonard Cohen was singing to in 'I'm Your Man' and if I knew, it wouldn't help my enjoyment of the song. There are certainly codes and references, stuff that's my own internal language. But I firmly believe that it doesn't help anyone's enjoyment of the song to know my intention behind it."
But Cara does appear on the record, with her vocals on the chorus of 'Pills' because her ex-girlfriend adores her "beautiful" voice.
St. Vincent said: "I knew it couldn't be my voice. Cara has a beautiful voice. It's just so pure. It's a sonic extension of who she is."
The 'Digital Witness' singer was shocked at the attention her relationship with the 'Valerian' actress received - and also impressed by how well Cara handles being in the public eye.
She said: "I'd never experienced anything like paparazzi following you in a high-speed chase down the streets of London. Not being able to walk down the street put a whole host of complications into [the relationship]. Cara is so kind and sincere that it didn't seem her spirit was corrupted by it."