I Became the Stepmother of an Irrevocable Dark Family

After dying in an accident, Leona wakes up in a novel as the third stepmother of the story's future villainess, Rebecca Petry. As Duke Ian Petry's only child, Rebecca is resentful, rowdy, and rebellious, terrorizing those around her. The duke orders Leona to raise his daughter, and she rises to the challenge, but the little girl is a formidable foe. To preserve the family's peace, Leona uses childrearing knowledge from her past life, but will she be able to turn this rugrat into a little lady?

“A romantic fantasy heroine possessed in a child care novel, ‘My golden baby!’”

Although the child care is a genre that heals the body and mind of a cute and lovely child who becomes the main character and is loved by everyone…
There seems to be something completely wrong with this genre I am in.

Even though it’s the age of glamor and regression, it’s hard child care.
The possessed Leona becomes the stepmother of Rebecca, the only child of the black family, who is the dreamer of a heinous evil woman.
She was a minor character who died after suffering from Rebecca’s intrigue, so I have to ran away somehow and try to save my life.

“You, you’re going to leave too, right? You’re going to abandon me like any other mother…”
What should I do when I feel weak after seeing a kid talking like this?

“You seem a little different. I need to keep you next to me.”
Why is the duke of black family has this reaction?

Can Leona survive in this world safely?