Was she part of the study?

If someone is left-handed, and left-handedness has been shown to be very strongly correlated with a different brain structure, would you challenge them similarly if they state that they have a different brain structure because they are left handed?

Do you need to personally participate in studies to know anything about your body?

I would if I were to undergo an invasive medical procedure.

Ah, I didn't realize how specific your use of "your" was, perhaps because she didn't make any claims about the structure of her own brain.