Think about it. Are you the same person in front of everyone? I really don't think there's a chance for debate here because you probably aren't.
A more formal way of introducing the topic of having different personalities would be to refer to the fact that we have different "circles". Let me help you set a scene: think about a wedding ceremony, and the couple getting married. Who are invited? The family; relatives – close and distant; neighbours; friends – childhood, from college, from university, and from that solo trip you took; colleagues – from your internship, the first job, the second job, your current job; and oh, the new in-laws. Talk about juggling greetings and forced selfies, the couple will have to interact with each of these "circles". And they'll have to juggle being different with each of them.
However, this isn't necessarily a disapproving human trait. It only goes to show you can read people, and can response according to how you feel. This is (almost) a survival instinct.
As long as you can be you, who cares?