Maybe 3? I'm partial to bother/sister incest, but "I'm so embarrassed just kill me" feels kind of dramatic, I think it might feel better if goes like "I can't imagine how I'll go to school tomorrow" and the brother suggests "what if you don't have to go", she's like "what do you mean?" and he's "say if I snuff you" and she'll be "oh, you're my savior!" Something along those lines would make it more light-hearted I think.