Who is Sarah Geller from King of the Screwups and what is their importance?

Sarah Geller, Liam's mother, is a former runway model. She now owns and runs Style Boutique in Westchester, New York. Described as beautiful and regal, Sarah has always taken Liam with her wherever she goes. Along the way, she has provided him with valuable lessons that provide him the talent he has for fashion and business. Sarah and her husband often argue over matters that have to do with their son, and she usually gives in to Allan's demands. By the end of the novel, she finally stands up to Allan for Liam.