There are three reasons that women play dumb on occasion. The first is because they are insufficiently attractive to attract men that they can look up to intellectually. Note that the author, who is an aged 3 at best, admits that the dim boyfriend to whom she refers was only the second man who had agreed to go out with her when she was in her 30s. It wasn't her brains that were the problem there. The second reason is because women understand on some level that most men prefer less intelligent women. This is not because men are intimidated by smart women, (think about that claim for a second, are they intimidated by male nerds and geeks?), but because intelligent women tend to be a quotidian posterior pain. Intelligent, educated, middle-class women are extraordinarily annoying because they seem to feel the need to constantly reaffirm either their intelligence or their education by pointlessly challenging those close to them over the most trivial minutiae. The fact that a more intelligent man can effortlessly slap down those challenges doesn't mean that he wants to waste his time doing so, especially when it interrupts his train of thought.
(To be fair, most intelligent people of both sexes are difficult compared to the norm, the significant difference is that women find the difficulty to be attractive due to their hypergamous nature. Men just find it difficult and don't want to deal with it.)
I found her cited example of a mispronounced word as an indication of a lack of intelligence to be more than a little amusing. In fact, those who mispronounce words on a regular basis are probably more intelligent than the norm because it indicates that they are learning words from reading them rather than hearing them. The writer has confused ignorance with intelligence; to the extent that a mispronunciation indicts anyone, it indicts the social circle around the mispronouncing individual who have never used the word around him. The assumption that "Arkansas" would be pronounced in the same manner as "Kansas" is a perfectly reasonable one, especially for an Englishman who is no more likely to know the difference between the two than the average American if it is Leicester or Worcester that is found in the East Midlands.
And the third reason is that women play dumb as an excuse to get out of things they don't want to do. Figuring out how to program a remote or change a tire isn't difficult, but why bother when you can simply get someone else to do it for you?