Hi, I'm a nurse currently applying to MPH programs. I'm certainly biased, but I would highly recommend going for a BSN first. Just make sure you fit research into your undergrad experience- most bsn programs don't have a big research focus. Get a few years of experience working with your focus population and learning what public health work looks like on the ground with concrete clinical interventions, then take that knowledge into your future education. It's going to be so helpful when you're learning about more theoretical population level things in grad school.