How does Mrs. Scorrier come to the realization that she needs to mend her ways in the novel, Venetia?

When Venetia's older brother marries Charlotte her mother, Mrs. Scorrier, is a part of the marital package. Upon her arrival, Mrs. Scorrier makes sure that Aubrey and Venetia are as uncomfortable as possible, causing trouble right up until the moment she realizes that she is alienating Charlotte in the process.