Secret Lady

Secret Lady is a Manga/Manhwa/Manhua in (English/Raw) language, Isekai series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.com fastest updating comic site. The Summary is

A child who has the ability to see ghosts, Yoon Seol-woo.
Has reincarnated into Rosantine, a princess who could see ghosts.
I've managed to fake not being able to see ghosts somehow but...
"Leave my sibling's body this instant!"
I cried out to the spirit who's possessed my one and only little (brother/sister)'s. However, only the death penalty awaited for me if my ability were to be found out. Then, there's only one way.
"You're planning to kill Prince Chartus, right?" I will save the Empire's second prince, Prince Chartus with this ability!
"I'll bet my life on Your Highness."