I'm going to have to agree with Preethi in regards with Catharine's status as the most minor major character in the story. She makes up 25% of our narrator's initial entourage and contributed nothing of interest to the storyline aside from another voice to be mimicked.

In all honesty she is kind of like one of those characters in Harry Potter who is prominent enough that when they die the reader knows things are serious, but the story continues moving along without anything more than a minor hitch.

A strange thing about Catharine's situation is that her role actually makes perfect sense given the time period in which the book is set. Her subservient, delicate portrayal is in sharp contrast to the independent (and seemingly historically inaccurate) Clara. After this conclusion it becomes apparent that Catharine's actions as a "major" character are completely normal and utterly average.