And her coach says 2:03 over 800m. Don't doubt him one bit.
I don't doubt it at all either.
Look at Ristananna Tracey. She ran 54.5 400H, 51.9 as a junior. She also ran a 2:03 as a junior. Note that to this day, 51.9 and 2:03 are still her PBs, but she was able to get down to 53.7 at 400H.
Anyway, McLaughlin is even faster than Tracey. So why not.