Hey MDmaybebaby!
I am currently in the process of completing a second UG to obtain a better GPA. What is your GPA currently? It may be worthwhile pursuing a masters degree and getting the additional 0.2 GPA added to your UG GPA as NOSM does.
I would think that NOSM would look at a masters degree as potentially more valuable than a 3rd UG. I suppose it all depends on you GPA's from your other two degrees (I would think a 3.5 or over would be pretty good since a masters would bring you to 3.7 or more).
I would definitely apply and see what happens. This is my first year applying to NOSM myself. I won't be done my second UG so they will be going off of my first UG GPA, but at least I can familiarize myself with the process while I finish off my second UG (currently holding a 3.8, plus I have a Masters for an extra 0.2). Just need to keep working hard and apply.