。
Mother always wears a kimono at home.
Literal
Mother [topic-は] always home [at-で] kimono [obj-を] is-wearing.
Two things stand out. 家で uses で (location of action), not に (location of existence) — one is doing the wearing at home, not existing there. And ~ている on 着る gives the resulting-state reading: 'is [in the state of having put on] a kimono,' i.e., 'is wearing' — not the progressive 'is putting on.' Clothing verbs in Japanese (着る, 履く, かぶる) all have this split.