Kojou Akatsuki
La Folia has strong feelings for Kojou. In the OVA she said that she will marry him instead of another man.
Kanon Kanase
Kanon is her aunt, and they seem to be on good terms.
Lucas Rihavein
La Folia currently has a disagreement with him about her suitor: she insists that Kojou should be her suitor while Lucas insists that she marry someone else. He even went as far as trying to engage her with a suitor of his choosing. Even in the end of the OVA, Lucas is still somewhat reluctant about considering Kojou as a potential future son-in-law.
Polifonia Rihavein
They are on good terms, and Polifonia trusted her enough not to mess up during the time she was at the terrorists' mercy in the OVA, believing that she 'knows what to do in this kind of situation'.
She also seemingly supports La Folia's decision to choose Kojou as her suitor.
Sayaka Kirasaka
Sayaka was her observer/bodyguard during her visit to Itogami Island. They seem to be on good terms.
Yukina Himeragi
They seem to be good on terms and rivals for Kojou Akatsuki's feelings.