Character Analysis
Mrs. Galloway isn't around all that much but she's worth mentioning for her supernatural abilities. This lady can see the future. Her son knows she only talks "if she's got something worth listening to" (12.58), and he wholeheartedly believes in her psychic prowess. Whether you believe in fortunetellers or not, there's no denying that she does predict a woman will save her son's life long before Serena enters the scene.
More importantly, though, Galloway believes every word his mom says—so when she says a woman will save his life and that he'll be loyal to her forever after, he buys into this hook, line, and sinker. His loyalty to his mom plays a crucial part in his subsequent loyalty to Serena. To not follow Serena like a pup would be to dishonor his mother and her psychic prowess and there's no way Galloway's going to do so. Too bad for him a better woman didn't save his life.