What are ways sexism was shown in this book ?

The standards of political correctness during the 1930's were definitely not what they are today. Just as Lennie was called "stupid" , Curly's wife had the same euphemisms for women thrown her way. This was a ranch populated by male labourers. Curly's wife was the only woman around and her manor had sexual undertones. The language that we call sexist was certainly considered "normal" for the time. In Curly's wife's case the many sexist adjectives would have been expected.