Shitsuji Shoujo to Ojousama執事少女とお嬢様 ; Girl Butler and her lady

Hinata is a student at a prestigious all girls private school and looks up to Tsugeyama Saki, the shining star of the school. As the younger sister of Saori, the head mistress of the school, Saki is the most popular girl at school with her warm personality, beauty, top academic skills and is pretty much the perfect girl. Hinata suddenly learns that her parents got extremely into debt, fled the country and pretty much left her out to dry. The headmistress Saori, out of compassion and seeing the Hinata's importance to the school, makes Hinata an offer to become a butler in return for providing room and board for her. Not having much choice, she accepts and is assigned to none other than Saki. Hinata soon finds out that Saki puts on a façade at school and is not the perfect girl everyone thinks she is. Source: MangaHelpers