。
She played a waltz on the piano.
Literal
She [topic-は] piano [with-で] waltz [object-を] played.
ワルツ is a routine European-loanword in Japanese, brought in along with the dance form itself in the Meiji-era westernization of music. Other dance-music borrowings followed: タンゴ (tango), マーチ (march), サンバ (samba), ボレロ (bolero) — most arriving directly through their Western names rather than being given Japanese equivalents. で marks the piano as the means of performance.