The first part sounds like a stretch, but how is it an over reaction? The sister is generally one of the worst I have encountered in a while and stated the reasons for it. The only thing childish was the older sister's behaviour.The sister should be way more mature. It's crossed my mind that the mom put her up this, to get a reaction out of the MC, which will make the sister see the light. In any case, the sister really should do her teasing and chastising in a much more subtle and mature manner. If no man can satisfy her, she really shouldn't be behaving like a teen. I agree with you somewhat, but I think your over-reaction is childish.