There are so many variables. You can work as a nurse for a school system and have school vacations off, or you can work in a long term care facility on a per diem/part time basis and basically tell them when you want to be scheduled and when you don’t. You can work for a large corporation and get the same vacations as everyone else (likely two weeks after your first year, three weeks after 5). I know traveling nurses who basically take a two week vacation at the end of every rotation (so three months in Colorado, two weeks to ski. Three months in Florida, two weeks at the beach). But those jobs aren’t for everyone, and you need to have a marketable sub-specialty for maximum flexibility (oncology nurses are usually in demand everywhere).
The job of a dietitian is pretty different from that of a nurse, so I wouldn’t pick a career based on vacation time. You need to actually like what you do!