I wonder was she brought up the way shes bringing Beth up, ie been told she's the best at everything and can do no wrong. Over praised.
I've a friend from school who's parents always told she she was the prettiest girl in school, the best at everything, better than everyone, always pushed and got the best parts on school plays. Don't get me wrong, I was praised as a child, but not to this extent and also praised my kids growing up.
She is now an adult and to say she's overconfident its an understatement. She would get her nose in anywhere. She reminds me of Denise, destined for bigger things.