I may be an only child, but I feel like I can chip in my 2 cents with my observations of the stereotypical scenarios are only as follows: you are the youngest and you are always believed by parents, or vice versa and you are always seen as the “annoying little one”. Sadly I don’t believe there’s often a middle ground. Now obviously from how everyone reacted, the eldest in this argument should easily be seen as immature and 200% at fault. She did not handle the situation well at all, nor (from the sounds of her past “act outs/records”) the past either.