Reincarnation: the daily life of a fan girl!

A story about a girl who lived most of her life without friends and without family love. She died due to her illness and reincarnates inside her favorite novel! "since I have a healthy body in this lifetime, I'm going to fan girl over my favorite characters!" Her plan was to spend her life as a side character watching over the main ones and to not interrupt the original story, but why is everything not going as planned!?