Senke school of tea ceremony
Refers to the tea ceremony tradition stemming from the Sen family, notably the Omotesenke, Urasenke, and Mushakōjisenke lineages.
She is learning the Senke school of tea ceremony.
From 千家 (Senke, the Sen family) + 流 (style/school). The Sen family name derives from the founder Sen no Rikyū's adopted surname.