Hero? I've Long Stopped Being One - Volume 1 Chapter 1

After dying from a strange terminal illness, Ling Lan was reborn into a world 10,000 years into the future. Although she dearly wished she could just live a peaceful and uneventful life in her new healthy body, fate had other plans…

Forced to disguise herself as a boy just so she could inherit her deceased father’s premium military benefits, Ling Lan’s journey to adulthood was full of challenges. After much difficulty, she finally turned sixteen when she could drop the charade. But before she could grasp her newfound freedom to get married and start her own family, a twist of fate results in her being thrown into the Federation’s top military boys’ school.

With these twists of fate, Ling Lan had little choice but to walk further and further down a path of no return, one of cold and aloof dominance…

- Description from Novelupdates

Through a mysterious portal, Chen Jin arrived at this strange place – a post-apocalyptic world where civilization had been destroyed.

She, the tribe leader of the Miaojiang witch tribe, was reborn as a pitiful little girl that everyone could bully.

I finally managed to kill the demon lord.