Zinnia Wormwood is the wife of Harry Wormwood and mother to Matilda and Mikey. She is the secondary antagonist of the novel and the tertiary antagonist in the film. When Matilda was young she would leave everyday to play Bingo leaving Matilda alone in the house leaving only an unprepared meal for her if she got hungry showing her to be a neglectful stepparent like her husband. It is also shown she uses hairdye since Matilda used it to punish her stepfather by putting some oil in his hair which resulted in him looking as some would say absolutely ridiculous.
One day she won a lot of money and used it to take her family out to lunch at a fancy restaurant which was the same day Harry took Matilda and Mikey to his workshop showing how he ripped people off. This caused Matilda to punish him by putting super, super glue in his hat which in turn stuck to his head which he couldn't take off at the restaurant despite Zinnia's complaints.
At the end before she gives Matilda up she confesses that she never understood her before signing the adoption papers! In the movie she seemed hurt that Matilda wanted Miss Honey to adopt her. However, in the book she couldn't care less.