How my BIG QUESTION relates to literature we have read recently

In The Stranger, Marie sacrifices herself in her love for Meursault. He does not reciprocate her feelings and is hurt by this. When she asks him to marry her, on page 41, he said, "it didn't make any difference to me and that we could if she wanted to." His lack of enthusiasm about their relationship seems that it would hurt her and although she is constantly smiling, it seems that this is a facade, masking her inner emotions.