She’s smarter than either of you thinks she is
I found this article rather disheartening. In short, it says that men tend to overestimate the intelligence of men and underestimate the intelligence of women. Even worse, women do the same, seeing men as more intelligent than they are, and other women as less intelligent than they really are. Given our human nature to live up to, or down to, the expectations of others, this constant dumbing down of women is very harmful to them – and to anyone who loves them.
Please, realise that your wife is smarter than either you or she thinks she is. Encourage her by regularly telling her she’s smart. Gently try to show her she’s not stupid when she says she is or acts as if she is. Stand up for her when others downplay her intelligence in any way.