Translation:Charlotte plays in a jazz orchestra.
You hear "jazz band" more often than "jazz orchestra", but outside of a small group that would be called a band no matter what they were playing, the difference between band and orchestra is the type of instruments. If it's a large group of people playing jazz and it includes a bunch of string instruments, then it's a jazz orchestra. If it's a large group playing without a bunch of string instruments, it's a jazz band. (One or two string instruments like a bass and guitar don't make it an orchestra.)
If it's specifically a brass band, in French that's une fanfare. Otherwise, French doesn't make the instrument distinction between band and orchestra: it's all orchestre.
When I looked up more about this, I found out that jazz bands started calling themselves orchestras so that people would be less likely to dismiss them because of racism. So there are some famous bands that are called orchestras. https://music.stackexchange.com/questions/3127/what-is-the-difference-between-a-band-and-an-orchestra
fwiw I would usually go with "jazz ensemble" in English, precisely because it's so general. Only when making a technical point like yours or referring to a specific group would I use the term "jazz orchestra" and I wouldn't suggest most ESL folks try to incorporate this subtlety as it would be lost on nearly all native speakers anyway.