RN career development path

Current state: Wife is a licensed RN. She qualified for the exam by completing AS in Nursing at a local community college. She also has a BS and an MS in Physics, which is far closer to engineering than anything medical.

Desired state: Several years ago, she got hooked on dietetics and healthy eating books. After trying a few tech things before going into nursing without much success and happiness, she thinks she now has found her calling. She loves this and wants to do food-related stuff professionally now. She wants to have the ability to eventually (after 10+ years of experience) have her own practice where she can see patients, order lab tests (blood, urine, stool, saliva, etc.) and prescribe medication if needed (none of the opioids or crazy schedule whatever stuff). Mostly, she wants to be able to point people in the right direction with food choices based on their specific needs, but the ability to order labs is a must.

How: There are 3 known options that I wanted to get some input on and, perhaps, any other available options.

1. Get a BS in Nutrition and then a Registered Dietician license. Based on the internet search results, getting an internship is really hard, getting a job is even harder afterward, may need to get a master's in Nutrition just to be employable, the pay is at best on par with RN if not lower. Unclear if RD's can even order lab tests and prescribe anything, probably not. Huge concerns about going through all this and being unemployed or underemployed afterward.
2. Get an MS in Nursing and become an NP. Much better employment prospects with both the ability to find jobs and better pay. Looks like NP's can partner with physicians and still see patients on their own, order tests and prescribe non-opioids? It could be challenging to get into the dietetics specialization, if one even exists, maybe?
3. Go to medical school and become an MD. Clearly, can do anything with your own practice, tests, prescriptions, etc. The only disadvantages are a long time and huge costs to complete this.

So, what's the most efficient way to accomplish the desired state here? Thoughts?