To your point, why does this quote undermine her narrative? She isn't saying she's saw herself as rational and others as emotional. Note that her use of "myself and others" in the quote clearly indicates that she's putting herself in the same boat as her audience rather that separating herself from them.
The former interpretation still comes across as quite condescending to me, especially after comparing to economists studying irrational behaviors.
The latter interpretation doesn't seem to match the text quite as well, but perhaps that was her intended meaning.
> I realized that I’ve overestimated my ability to quickly understand what drives people to do what they do. I have overvalued reasoning in myself and others and undervalued pride, fear and the need to belong.
The context is "what drives people to do what they do", and she used to work on the assumption that what drives most people is mainly reasoning rather than emotions. But she discovered that this isn't true, including for herself.