With any performing art, sh will find that everyone wants to go to the brightest and best school, the most connected teacher, the very best training. It's just common sense. If these three girls ( your daughter and her 2 friends) are all serious about a dance career then they will dog her every step of the way.
Every major audition I've ever been to (I'm an actress not a dancer) I've wished certain other people weren't called or worse still invited without applying (because that means you're in the also ran stakes if the invited's don't accept it for any reason). However, it pays to be nice, warm and inclusive under such circumstances or you soon get a reputation for being a diva, and then people don't want YOU around. She'd do well to smile, welcome them and understand how performance art works, and as she's eight you need to help her do that, because one day one of her friends might do well and be able to help her up, that's the way it works, you can't always be the focus yourself.
If it's not something she seriously enjoys and it's all for giggles then find her something else she enjoys and don't tell her friends but she needs to address this aspect of her personality otherwise it'll cause her grief later on. x