Marie's Love

Throughout The Stranger, we get accounts of Meursault's relationships with others, including that with Marie. Marie and him seem to have a slightly complicated relationship, in that Marie clearly loves Meursault, and he recognizes that he does not feel the same way. Yet they stay together. Or more specifically, Marie still stays. It's unclear just how much Meursault is holding onto Marie, whereas it's obvious how much effort Marie needs to put into the relationship to continue it. In this way, Marie almost perfectly portrays how some women feel obligated to stay in relationships that may not be healthy to "save the man". In Marie and Meursault's case, the unhealthy relationship is characterized by how uneven the give-and-take is: Marie gives so much more to it than Meursault does.
The first example I immediately think of is how Marie asks multiple times whether or not Meursault loves her. His answer of not knowing, but probably not obviously is not what Marie wants to hear. After all, she herself had just told him she loves him, which implies that she wants to hear that he feels the same way. Though it's not explicitly said, this answer probably hurt Marie, and yet she continues to go back to Meursault afterward, and even talks about marrying him. Meursault seems indifferent to the prospect of marriage, saying they'll get married if she wants to. To me, it seems like Meursault would be indifferent to Marie staying or leaving, and it is up to Marie really to keep the relationship going.
Another example of this is when Marie comes to Meursault's trial. At first, she is just observing the trial, almost acting as an emotional support. Then she actively becomes a witness and defends Meursault, even crying on stand for him; crying because of how the court is twisting her words against Meursault. She tries to protect him, to save him, and the court is working against her. Still, she has hope for him, and even says that they'll get married once he gets out. She writes him letters fora  while as well, obviously showing how she is trying to keep contact and maintain a relationship, maybe even to give him something to look forward to when he gets out. Yet after she stops writing and visiting, the only thing he thinks about her is that he didn't really care if she was dead or a live. Granted, he was in a situation where it wouldn't ultimately matter to him objectively, but this is still a cold kind of statement to make.
Marie obviously doesn't like the current relationship the two of them have, yet she continuously comes back and tries to change it, and essentially change Meursault, for the better. This in the end only brings her sadness as she watches the man she thought she loved get condemned to death. To me, it seems evident that Marie would have been much happier if she had let Meursault go early on and found someone who could reciprocate her feelings, but because of the obligation she felt she had to defend Meursault and stand by him, she caused herself suffering.