Andou Mai

Rio, the transfer student, will have a destined meeting with one of the Sanrio guys but..!? (from mangaupdates)

The life of Floria, the daughter of a poor baroness, has been drastically changed by an oracle. Her sister Renata, who was supposed to be shy, changes her attitude after being chosen as a saint, and for some reason she begins to see Floria as an enemy. In order to escape from Renata, Floria is sent to work as a servant in a nobleman's mansion, where she meets the most beautiful duke, Desiree. Floria's daily life changes dramatically and vividly after meeting him.