i understand what you're saying, but she will have easier success at 400h compared to 400m.
right now she is at least .5 second better than any other woman in the world at 400h, probably more like .7-1.0 better. her level of success (winning medals, setting records) in the 400h could span 10-15 years. we could be talking about her on this message board in the 2032 olympics because she is just about to turn 19. historically, there isn't as much competition in the 400h as the 400m which is why her dominance could last so long. her path to long sustained success is so much clearer and easier in the 400h.
now in the 400m she is definitely not the best right now. i would bet on miller and naser over her and there are a slew of other young 400m runners like wimbley, ellis, irby, etc with similar ability. miller and naser aren't exactly on the downside of their careers. both are looking like historical talents with only 10 women having ever broken 49. like everyone else, i think mclaughlin can break 49 but there are potentially 3-4 others who could do it in the same race in the next few years.