Instead of analyzing Vera Brittain's life as a kind of existential argument, the reader might consider that to Brittain, each moment in time was experienced in real life, in real time. This issue is raised by the gravity and horror of the WWI battle scenes, but it isn't fiction, so the reader must resist their urge to categorize these events as fiction. By experiencing WWI, Brittain changed her degree from English to History, literally. She decides that in light of the absolute horror of warfare, she ought to concern herself with the past wars.
In many small ways like this, Brittain's behavior can be clearly seen as the strategic response to the situation. She learns about education and sees clearly that, even though women don't really get to go to school in her culture, they do already get to go to school somewhere else, so she moves. That tenacity serves her well in life, but it is also responsible for her brave decisions to go to war, to sacrifice her life and her mind for her nation, even a nation that doesn't care about her mind in the right ways, because of the prevalence of misogyny.
Ultimately, this is the most important aspect of Vera Brittain's feminism. Hers is not an opinion that she made up somehow. Her father's opinion was that by imposing social rules onto women, that life could be made easy for women, and that they needed life to be made simpler for them. This is clearly a psychological projection about his own lack of control in life, and although he wants to protect her, his hatred drives Brittain to unimaginable horror where she learns, like the Buddha, that no one is allowed to be insulated from horror and pain, so we should all respect everyone's point of view. When her husband agrees with her, this argument is complete—they are evidence that the new way works just fine.
