There are many threads on this perennial favorite topic on here that go back aways. I encourage you both to browse the USNA forum and use the Search function.
There is a path from USNA, though a narrow one. USNA is designed to produce warfare officers, not staff officers (doctors, nurses, lawyers and a few others). It's usually anywhere from 13-17 per year out of 1100-1200 in a class who are allowed to go to med school. When I sat on the USNA board that reviewed the mids' applications near the end of junior year, I recall we reviewed over 60 packages. The class standings were very high, with no major conduct incidents or performance issues. MCATs had to be in a zone that ensured acceptance at at least a few medical schools. There is no guarantee. If the mid doesn't get approved, off they go to ships, subs, etc. There are briefs on this at USNA early on. Most are Chem majors, but some are other majors, including liberal arts. There are advisors who help them with their schedule so they get the life sciences they need, often giving up summer training blocks to get it all in, or volunteering at a military hospital to improve their application. This path is NOT for the person who wants to be a Navy doc and nothing else.
They must take MCATs and get accepted to med school on their own. Navy will pay.
After USNA, the approved grads may go to USUHS, the military med school on the Walter Reed NMMC campus, in full active duty status, or attend civilian med school in an inactive Reserve status with stipend. Look for kp2001's post on how the years of pay back stack up. USUHS usually accepts Service Academy grads.
Or, attend civilian college, explore Navy HPSP program for medical school, a very nice way to go, and how the majority of Navy docs get their commission.
Or, attend civilian college, apply to USUHS directly.
Or, go to USNA, NROTC, OCS after civilian college, go a regular warfare officer route, get out, use GI Bill or HPSP to attend medical school, apply for Med Corps commission, return to active duty.
I am not commenting on NROTC>med school, because I don't know what happens there.
Do not overlook the Public Health Service Officers programs. They are a Uniformed Service with most of the same benefits as the Armed Services, and are very professional. They have some scholarship programs. Their uniform is essentially the same as Navy, with different crest and professional insignia.
It will take some research to lay out all the paths in terms of risk, cost, payback time. I am sure the military docs who post here will comment.
http://www.usphs.gov
https://www.usuhs.edu/medschool
https://www.navy.com/joining/college-options/hpsp.html