Rare to see the FL's relationships with other men written so well and beautifully and for it to still not even come close to charming me as much as her relationship w the ML, but The Devil's Lady hits it out of the park.
Erez is the perfect foil to Diabel in season 1. While Diabel is sinister on the surface to cover up for his deep and unwavering devotion to Ayana's happiness, Erez is sweet and pure on the surface but the poison of who he once was lurks in every interaction he and Ayana have. He's brilliantly written in my opinion because, regardless of if he truly does hide something sinister like Ayana suspects or if he does just love her purely, every single one of his interactions with Ayana only reaffirm to the reader her love for Diabel. She is constantly yearning for Diabel in every interaction with Erez, and she is never swayed by romantic interest in Erez, but rather by empathy with his love for her and the way it mirrors the yearning she feels for Diabel. Through Erez, the reader is able to see just how attached Ayana is to Diabel over and over and over, and it is reaffirmed that she doesn't have it in her to love anyone else.
We also have Rox who, in another world, could be an incredible 2nd ML. Rox and Ayana have countless scenes together where they finally relax. Each of them find a kindred spirit in the other and constantly cheer each other up and defend each other. It is so refreshing that Ayana is able to develop such a close, familial bond with another man without it descending into the angst of confusion or yearning. The respect and care they have for each other is genuine and earnest, but the narrative doesn't turn this respect or care into the romantic tension that is typical of any relationship between a man and woman in a romance story.
Ultimately, every scene Ayana and Diabel has together truly beats every other scene in the story by leagues. The depth of their devotion to each other is plain as day EVEN AS Ayana questions Diabel's motivations and affection for her. It's a brilliant setup because you have all the angst of a noble commoner relationship and all of the devotion of a knight princess relationship, but there's the refreshing twist that Ayana belongs to Diabel after their deal while Diabel belongs to Ayana as her knight. The power dynamics between them ultimately puts them on equal footing as they each yank the other around without being honest about their depth of love for each other