The interaction between Connell and Marianne in this scene serves as a good reminder that they’re still rather young and inexperienced when it comes to love—after all, Connell claims that he’s in
love with a person he’s only been dating for a month and a half! Of course, it’s technically possible to fall in love that quickly, but it’s pretty rare. It’s also possible that he’s just saying he loves Helen as a way of making Marianne jealous, maybe because he hates that she’s dating Jamie. Either way, though, there’s a sense of emotional immaturity at play as they talk to each other about their love lives, since neither of them are capable of simply stating the obvious: namely, that they love each other and want to be together.