I thought she was the right person for the position, yet it turned out that she was quite useless.

A Contrary to my initial impression, she was not totally unsuitable for the position

B I was right in my thinking that she was totally useless for the job

C I was mistaken about her suitability for the position, since she proved rather incompetent

D Because I was expecting her to be competent, I was shocked to see her perform rather badly.