Cattleya de la Fontaine

Cattleya Yvette la Baume le Blanc de la Fontaine (カトレア・イヴェット・ラ・ボーム・ル・ブラン・ド・ラ・フォンティーヌ, Katorea Ivetto ra Bomu ru Buran do ran Fonteinu) is the older, and seemingly favorite, sister of Louise de la Vallière.

Background
Cattleya is a very gentle woman who thinks positively of Louise. She knows Louise very much, and she knows that Louise is madly in love with Saito who was a plebeian. Despite his status, Cattleya approves of their relationship. Unfortunately, she is bodily unstable and has an illness. She is the head and only member of the House of La Fontaine.

Cattleya attended Louise's and Saito's marriage together with her mother and her elder sister.

In the light novel, Cattleya called upon the water spirits to heal Saito's wounds caused by her parents. This presumed that she has also an magical affinity for water.