The symbolic father
The disapproving father is in this story, a literal human being, Brittain's real father. But because of his point of view and its extremist qualities, he also represents a kind of symbolic psychological issue, the feeling that one's parent doesn't understand the latent potential within one's self, and that they are harming the growth of the child by restricting their access to approval. For Vera, the limitations were because her father held misogynistic beliefs about women and their competence.
The symbolism of horror
There is a clear motif in this story of horror, because Vera Brittain's real life is being reported, and in her real life, she was made to endure a long season of absolute panic and death fear, because she was in WWI as a nurse, and they were constantly under threat of attack, and indeed many of her friends died in combat. Meanwhile, she was made to try helping people who had been damaged in new ways that had never been conceived before, like by a tank or machine gun.
The symbolic switch in major
When Vera goes back to school, that is a symbolic decision. She realizes that the season she just endured doesn't actually help her adjust well to society, but instead leaves her with PTSD, so she becomes a historian by education, switching to that so she can study the past. This represents her newly established relationship to post-trauma and to the reality of warfare. One might say she has an objective appreciation for the value of history.
The symbolic friend
Without someone to connect with, Brittain spirals into panic. Winifred represents Brittain's need for social connection. In a way, he also symbolizes her serious emotional issues around connection and intimacy, because she was made to fall in love with all her friends just to watch them die in battle, and she doesn't know if anyone will ever love or understand her, but a single friend gives her hope by connecting with her about writing and about the need for peace.
G, the saintly husband
If Brittain's depiction of her father frames him as a kind of poor role model for men, then certainly, the last stories of the novel are designed to suggest G as a role model, because when she tells him that she will need to be free from traditional marriage roles, he accepts her and she loves him for that. This demonstrates a new kind of dynamic between her and men, because she has enough trauma and experience that she cannot afford to operate in any other way than to stand up for herself with honor and self-respect. He loves her for that.
