I believe the term ‘personality’ is used incorrectly in everyday language.

When people talk about personalities it is usual in fixed terms. An individual is one way and will always be that way. “It’s just her personality” they might say.

But then how do you explain a person who stammers who used to be shy, but now can’t stop going out and socialising?

I think it’s better to think of ‘personality’ as being time and context dependent.

Asking the question, what is this person like in this particular situation is better. Because a situation isn’t static. In another situation the person might have changed and will behave with a different personality.