We never get a direct insight into Maggie's mind, but we can infer quite a lot about her from the way she acts and what her mother tells us about her. She appears extremely shy and retiring as a result of the burns she suffered in the house fire, as her mother reveals. Her mother describes her gait in the following terms:
Have you ever seen a lame animal, perhaps a dog run over by some careless person rich enough to own a car, sidle up to someone who is ignorant enough to be kind to them? That is the way my Maggie walks.
This image of the wounded animal perfectly captures Maggie's self-effacing and nervous manner; it seems she is a person that other people simply ride roughshod over, pass by. She hardly speaks at all, tries to keep out of sight - and in this she forms a complete contrast to her older, brash, confident sister Dee.
Maggie, however, does have strong feelings of her own. We see this in her disapproving reaction to Dee's visit; the noise she makes when confronted with Dee's extravagant fashion sense. She also slams the door violently when Dee first asks for the quilts that have been promised to her. However, she appears anxious to avoid confrontation when she says meekly that Dee can have the quilts (although her mother does not allow this to happen).
To sum up, we can deduce that Maggie has had rather a hard life and has become withdrawn as a result. Yet there is also a hint that she is, after all, fairly content with her quiet and modest lot; she smiles when Dee ends her unwelcome intrusive visit, and then afterwards she is described as relaxing contentedly with her mother until bedtime.