Who sat in the seat opposite Helen on the train?

In chapter 9 of The Story of My Life, Helen is on her way to Boston, traveling by train with Annie Sullivan to the Perkins Institute for the Blind. It's a very exciting journey for Helen. She's made so much progress in engaging with the world around her since her journey to Baltimore two years previously. Then, she was restless and agitated, requiring constant attention to keep her amused. But now, as her train glides alongside the beautiful Tennessee River, she's quiet and relaxed, taking in the vivid descriptions of her surroundings spelled out on her fingers by Annie.
As well as Annie, Helen has another companion on her trip: her large rag doll, Nancy. Nancy sits on the seat opposite Helen and Annie in her new gingham dress and a beruffled sunbonnet. Whenever Helen finds herself no longer absorbed in Annie's descriptions, she suddenly remembers Nancy's existence and takes up the rag doll in her arms.