Well, again, I think it's important to remember that the war is over at the time that the film takes place. And, in any case, the war would be a current event that she lived through, but she would have experienced the war in a very detached way... through news stories, encountering soldiers/ veterans, etc. And as I posted before, people go about their daily lives all the time during wartimes and in the wake of war.
The fact that she ends up being a wife and "a perfect hostess" as Peter predicts about her in her youth... is in a way a sad thing. She thinks of herself as "Mrs. Dalloway... not even Clarissa anymore." Her identity and the direction of her life has been driven by her class and social expectations. In her youth, in the movie, you hear her talking about the world seeming very dangerous... and her main concern often seems to be safety and security. Her preoccupation with being safe, actually reminds me a lot of Ennis. They both choose what they believe to be a safe path over more risky paths that probably would have led to greater happiness.
In a way, I think the film/ book is a lot about how life can turn out somewhat disappointing... Sally Seton wanted to change the world when she was young (with Clarissa's help)... but instead both women ended up in very conventional roles. Peter's life turns out to be a "failure" too... he wanted to be a writer... but at the party he reveals he hasn't written a word... and his life seems consumed with social scandals.
There are scenes from Clarissa's youth where we see how unpleasant and conventional Clarissa could be... for example, her attitude about the woman from a lower class who had a baby. But, I think we're supposed to understand that Clarissa had a lot more potential in terms of intelligence and sensitivity... a lot of which she squashes, again, for the sake of convention. I think, again, like all the characters, she's meant to be seen in both positive and negative ways. She was bold enough to kiss Sally, but nowhere near brave enough to really pursue that relationship. Though, from the perspective of a lesbian viewer/ reader, it's interesting to hear her muse at the end that she may have forgotten or overlooked (I'm forgetting the exact wording at the moment) the thing that mattered most to her.