Kirawaremono no Reijou wa, Watashi ga Aishimashou. Imasara Dekiai shitekitemo, Mou Osoi desu!

After dying alone, office worker Aki awakens to find her soul inside the body of a noblewoman named Isabelle, a girl from a powerful ducal family. Isabelle was known for being arrogant and hated by all—Her family ignored her, and even the one she loved coldly rejected her. She died unloved, with a shattered heart. But Aki, who also suffered from loneliness in her previous life, made a firm decision: "If no one else will love her... then I will." However, she soon starts noticing strange things about the people around her...

(Source: Kodansha, translated)