Currently an Army Reserve First Sergeant and 2 years away from receiving a BSN. Should I stay Enlisted or become an Officer?

If you plan on practicing as a nurse in the Army you have no choice but to pursue a commission. they will not allow you to fill an ANC position on the mTOE or TDA as a 1SG, even if you do have the credentials for it. If you don't plan on being a nurse in the Army, and only practicing as a civilian, then at this point in your career, there really is no point in switching over.

As others have said, you need to make sure your decision aligns with your personality and goals. Also consider how much time you have left before retirement - as an E-8 you obviously have several years in. How much longer do you want to serve? Which career track (enlisted vs. commissioned) offers you the best opportunity to continue to serve and further your career? As an E-8, I would imagine you might be getting close to your ceiling for career and promotion opportunities which would make the commissioned track more appealing. BUT, as an E-8, your retirement pay is more likely higher than that of a junior commissioned officer. Can you serve another 8-10 years to gain the rank to make a difference in retirement pay? Are you willing to be viewed (as a junior officer) as you have viewed other junior officers? Big changes going from senior enlisted (respected) to junior officer (unfortunately often times viewed as "clueless" and "bumbling").

This is something my wife is looking into right now. She's a Reserve Staff Sergeant who's about to finish her BSN in less than a year. I called AMEDD recruiting on her behalf to get the lowdown.

--First, Direct Commissioning into Reserve Nursing requires the BSN plus a minimum of 6 months work as an RN. You can't even submit the packet until then, though you can prep a few months in advance. They will also need references (civilian and military), all your past 214s and awards, and a whole bunch more for the packet. They even have to re-process clearances, even if you already have a TS/SCI. And though it's rarely a problem, you must have at least a 3.0 GPA as the cutoff for applying.
--Second, you would qualify for O1E-O3E in place of normal O1-O3 pay, but in all honesty you'll probably also qualify for saved pay (per AR 37-104-4 Ch. 3-4) so don't worry about the lower pay scale for junior Officers -- you won't lose a penny.
--Third, if you serve less than 8 years commissioned (which can include IRR) before transferring to the retired list, then you'll lose your commissioned rank for retirement and revert to your highest qualifying enlisted rank. If the Officer rank you reach turns out to have better retirement, better to wait out the 8. (Note: I'm pretty sure there's a waiver for this if you are medically retired before 8 years commissioned.)
--Finally, as others have mentioned, ultimately this comes down to what direction you want your military career to take. If Nursing in uniform is what you want, and you're willing to put in the time (and remember that the time won't start until you commission, which is still 2.5 years away at a minimum) jump at it. Otherwise, just retire at E8/E9 and have a good civilian career as a nurse.