Helen is Catherine’s friend. Her personage is quite interesting as she doesn’t play a role of a woman; she is more a personification of a parent. We mean that she’s a parental figure to Catherine and is very protective of her, maybe such kind of friendship is not as much strength as the one Henry and Piani had, but it definitely deserves to be highlighted.
Helen is a Scottish nurse. By the way, hearing the profession “nurse,” we immediately realize a good woman who has the only desire – to help. In some way it was true, she is really helpful, honest, reliable and always ready to serve. Catherine and Helen get acquainted exactly on the war, and exactly the war made them very close friends. As the novel goes on, we see something strange. Isn’t it Helen who completely falls in love with Henry even knowing that he is the love of Catherine? Yes, here we are.
At first, she appeared to be a very good friend, who supported Catherine in her struggle to be with a man who she doesn’t know. But with some time her woman inner world showed itself – she started being jealous of being incapable of hiding it. (Yes, Hemingway’s reference to his love to women, because yes, really, it is the only thing we do – have sex, cry, and feel jealous. Hemingway, it’s not cool!)
As Helen later grows jealous of his and Catherine's relationship, she fears Catherine will abandon her. Her hysterical outburst over Henry and Catherine’s “immoral” affair establishes her as an unhappy woman who is paranoid about her friend’s safety and anxious about her own loneliness. That is why she is a parental figure of the book for Catherine, on the one hand, she wishes everything good to Catherine, and on the other hand, she can’t make up mind to the future relationships of her best friend.
Helen Ferguson in the Essays