While there are tons of bio majors who don't get into med school, there are tons of bio majors who do! And plenty of other majors too! And there are plenty of other good careers out there.
She might not be happy as a lab tech in a hospital. But she may decide to get a PhD and pursue a research or academic career, or she might love working on health policy or going into social work and advocating for pts, etc. If she majors in bio and decides she wants to be a nurse, there are lots of programs that will allow her to do so.
Which is why its important for her to pursue a major she is passionate about rather than one that will prepare her for professional school.
My advice would be for her to go to the schools she is interested in (if you live far away tell her to just pick a few favorites), sit in on classes, spend a night in the dorm if she can, eat in the cafeteria, etc and see where she feels most at home. If she is happy, she will thrive and suceed regardless of the school or her major.
Does she have until May 1st to decide where she wants to go? If so, maybe she could spend some time shadowing - spend a few days with an in-patient nurse, a few afternoons with a NP or PA. When she goes to visit colleges, maybe a professor or two will talk to her about his or her research and academic career.
Finally make sure she is making the decision for herself. She is the one who has worked hard in HS (and previously) to have this difficult choice, and she is the one who has to live with the consequences of her decision. While you might think that a school and major is best and as parents its your role to give her advice and help her decide, its ultimately her choice.
Finally, I think it would be very hard to do nursing shifts during med school! Maybe during vacations and breaks, but most weeks I had enough trouble just keeping up with my coursework without being on my feet for 8 or 12 hours over the weekend working really hard caring for pts!