This bugs me so much. Vulcan is established as having higher gravity and thinner atmosphere than earth. Sure humans could stay there for short periods, but an extended stay - especially after Burnham had already gone through her first growth spurt - would be devastating to a human's health.
They also demonstrate exceptional mental acuity - to the point that Spock took 3 tests simultaneously - which I'm sorry, not even the smartest human on earth can quite replicate. But no, not only is Michael able to thrive on the planet without medical aid, but she even beats out native born vulcans to be top of her class.
I've had arguments with other spergs over whether Mikey is a vulcan or not (no joke, one reply was "she's a vulcan culturally, just not biologically"). That's what angers me most about her. She's turned one of the classic aliens of Star Trek into just a cosplay*.
*I mean it makes a bit of sense with the Klingons which are a more spiritual people, but the Vulcans are supposed to be logical.
EDIT: I should also say, it would be fine to have Mikey work her ass off just to not be the bottom of the class. Give her something to struggle against her whole life, she might have been a compelling character then.