If you daughter wants a bachelors in nursing (BSN), she can't do the "bachelors" part first and then go back to the "nursing" part. And while she could do another bachelors while she waits to turn 18, she will still have to attend a nursing program
(BSN (traditional or accelerated), ADN or diploma) in order to become a nurse. Nursing is not an add-on program that she can decide to do on a whim. Nursing school has both theory/lecture and clinicals integrated in a specific way--one can't pick and choose what classes according to their own timeline.
In addition, clinicals start almost immediately in nursing school, and can't be missed. Keep in mind that almost no hospital wants a minor doing clinicals on the floor...too much liability. Volunteering as a candy striper as a teen is one thing, but nursing students are assisting/performing procedures, giving medications and are responsible for patient care.
She could start knocking off pre-requisite/co-requisite classes such as Anatomy & Physiology, Microbiology, Public Speaking/Communication (yes, very much required), Statistics, Ethics, and other non-nursing classes. But for the actual nursing program, she most likely will have to wait until she is 18.
Sorry if this isn't what you--and she--want to hear.