。
She loves playing the koto.
Literal
She [topic-は] koto [object-を] play [thing-こと] [subject-が] very like [is-だ].
琴 (こと) is a thirteen-stringed Japanese zither, one of the most iconic traditional instruments of Japan — central to gagaku court music and a staple of New Year's broadcasts. 弾く is the same verb used for piano and guitar (string and keyboard instruments). The full structure here — ~することがとても好きだ ('very much like doing X') — uses こと to nominalize the verb phrase, then が-marks the nominalized clause as the thing liked. 好き is a な-adjective taking が for what's liked.