The coach (according to the author) made that call based on her assumptions about the hire based on his gender, age and geographical origin. That's not informed personal opinion, it's exactly the kind of discrimination which the author is complaining about.
a) There is such a thing as cultural awareness. It is not the same as discrimination. If you travel a bit you find that there are actual differences between cultures. If you use those differences as justification to treat individuals unfairly then that is discrimination. (If you use false stereotypes as justification to treat individuals unfairly then that is also discrimination.) Discrimination is about how you treat individuals, not about being unaware of general trends. In this case, since the author's interaction with this individual is in the past, neither she nor her coach is discriminating.
b) The coach, according to the author, made that call after she recounted the story. Presumably in a lot of detail, and after numerous other coaching sessions in which her coach would have built up a detailed picture of how she worked and where her weaknesses lay.
Elaine Wherry lives in Bay Area. Is gender discrimination a huge common problem there?
All she has is a guy refusing a job offer. After that she talks to some radical feminist who decided it was because of her gender, and she, for some strange reason, accepts that explanation as truth and shifts all the blame to the guy.