Answer:
If someone is around their best friend who knows everything about them, they are probably going to act like themselves because they really don't have anything to hide; they don't need to impress their best friend. However, that same person is going to act completely different around their crush because of course they're going to care what their crush thinks of them. They might try to act cooler, sweeter, or kinder in order to impress their crush; this is the kind of behavior that was not expected in front of their best friend.