First few exams and I had WAY better marks than all of them, lol.
(As a side effect of this, one could predict that approaches to mitigation of impostor syndrome (which there are a few of) will be especially helpful if you're concerned about improving women's representation. Somewhat ironically though, the "ideological echo chamber" that is most active in pursuing these goals is not always very open to such notions!)
Someone who is well aware of how complex a subject is can find a given class to be easy, which would imply they are not under the Dunning-Kruger effect. Confidence alone is not sufficient.
Edit: that they ended up with lower marks due to not studying due to overconfidence due to the earlier ease of the topic seems like it would fall under Dunning-Kruger.