Read manga: A Match Made In Mana

Manhwa
Summary:

Lilienne Islar died an abusive mother, a neglected wife, and a cast-off stepsister. So when she suddenly opens her eyes again as her younger self, she decides to set things right with the people in her life. Luckily, her stepbrother's a secret softie who's easy to win over. Her fiancé, on the other hand, is a magic-powered war machine doomed for insanity. With an illness draining her mana daily, will Lilienne have the strength to save her future husband and maybe even the whole empire?