I'm still in high school but I am considering studying to become a dietician/ nutritionist when I graduate. I do biology as a subject and the university I am hoping to go to recommends at least one if the sciences as a prerequisite. But would chemistry be needed in the course? Also is the course hard?what is the annual salary of a dietician? And where is easiest to pick up work? Hospitals? Private practice?

Normally the required courses will be that of the university. Foreign language often for many, Algebra, both biology and chemistry. You need to check on the specific school that you want to go to, each university has its own requirements.

Nursing homes, hospitals, private companies that provide those services,
Are all companies that would be possible. And you get hired, it is a job or career and finding work anywhere in any field can be hard at times. So be ready to compete for work