Are You Saying I’m Going to Become the Favorite Daughter-In-Law?

I found myself reincarnated into a spin-off where my favorite character from the novel dies and her son becomes the male lead.
Of all things, I’ve possessed the villainess who dies a wicked death by execution, the fiancée of the male lead, Lyla Brilston! The only fortunate thing is that it’s still the male lead’s childhood.
“I refuse to die like this! First, I’ll crush my death flag and then try to save the life of my favorite character!”
By using information from the book, I managed to assist the Northern Alliance and befriended the male lead, who was as icy as a spear.
Unlike the original Lyla, I even gained special abilities and intended to peacefully indulge in fandom….. until suddenly, the male lead starts interfering with my fangirling?!
* * *
After the coming-of-age ceremony and meeting the female lead of the spin-off, it seems it’s my turn to step back, so I offered a divorce decree to Calix. His eyes grew cold at the sight of the divorce decree.
“Divorce? Who decided that?”
“We were engaged, remember?”
Calix ominously froze the divorce decree before burning it again. The divorce decree vanished like an illusion.
“So, you’re just going to leave me and go to someone else? You’d rather fawn over our mother? Go ahead. I have no intention of letting you go.”
The only thought that came to mind at the sight of Calix’s persistent gaze was one. It seemed that I had twisted the original story too much, causing the male lead to seem subtly insane.