When you fight with your partner but you still love him, this is what it looks like. This girl was mad at her boyfriend, but for some reason, she still felt obligated to make his lunch, like she does every day. This isn’t much of a revenge, since she still made his the sandwich, but at least she let him know she was not happy about it.
Perhaps this note will make him feel bad about himself, and that’s the revenge behind it, and perhaps there’s no revenge here – she simply wanted to let her boyfriend know how she feels. Either way, we feel like this conflict isn’t resolved, and they’re going to have a long conversation when they get home.