How would you handle girlfriend who is a showoff?

Guys how would you handle an issue where your girlfriend is treating you one way when you are alone with her and when she is with her friends she is a totally different person, like she ignores you or she acts really bossy whenever her friends are there? One guy who I was hanging out with yesterday said that he told his girlfriend privately right then and there that he sees that he hates when she is acting like two different people and that she doesn’t know how to be one person and she got into a fit and walked out on him. How would you handle it in a way to save your relationship?