。
She's interested in jazz.
Literal
She [topic-は] jazz [in-に] interest [subject-が] exists.
ジャズ entered Japanese in the early 20th century with the music itself — Tokyo's interwar 'Jazz Age' (ジャズ・エイジ) saw a vibrant scene around dance halls and cafés before being suppressed during WWII as enemy music, then revived in the postwar period. The pattern ~に興味がある is the standard 'have interest in' construction — note that the source of interest takes に, not the more intuitive を. Literally 'in X, interest exists' — Japanese frames interest as a relationship to the object rather than something you have toward it.