Who is Clarissa from Little Bee: A Novel and what is their importance?

Clarissa is a good friend of Sarah's and works with her at the magazine. Clarissa pushes Sarah to publish fluff articles, often talking her out of the more hard hitting articles in order to support their readership. When Sarah takes time off for her husband's funeral, she returns and finds Clarissa firmly entrenched in her office. However, it is Clarissa who urges Sarah to change her mind when she decides to quit her job.