Hakkou na Koushaku Reijou (Byoujaku) ni, Nokori no Jinsei wo Takusaremashite: Zense ga Kinniku Mojo nanode, Oujisama no Kyuuai ni wa Kizukemasen!?

Synopsis

Reincarnation in another world from Kureha (martial arts office lady) to Kureha (a sickly daughter of a duke)!! Despite going to a new world, Kureha could not overlook evil. Thus, her display of physical might contrasted with her appearance (in a good way), and the prince of the neighboring country who was there shared a secret with her... (Source: Kadokawa, translated)