Saisei Mahou ga Kiki Sugita!: Jinsei Yarinaoshitara, Ousama ni Natta moto Buka ni Dekiai Sareteimasu

Neglected and abused for killing her mother in childbirth, Patricia Alben leaves home at an early age to join the army, where she thrives thanks to her exceptional mana. There, she meets Theo, a bastard prince assigned to her unit. Pity turns into closeness as she trains him, until they’re sent on a suicide mission where Patricia is gravely injured saving Theo. Healed by Theo’s magic, she awakens as a child and is adopted by her former family. Meanwhile, Theo slaughters his own family and claims the throne… (Source: WEBTOON)