For me, I thought that this person was a friend and a good person for a long time. I trusted them (and I don't trust people easily) and it turned out that I was wrong to have trusted them. I pretty much cut them out of my life once I found out the truth.
Re: introvert vs extrovert: I think that I'm an extrovert to a certain extent. I'm social and can pretty much talk to anyone, but I'm also very private. I don't often reveal a lot about myself; especially not to people I don't know well.
I used to be a very shy, quiet person. Now, not so much.
This sounds exactly what happened to me!! However this was a complete stranger who I got to know so well in the course of a few weeks as we hung out all the time. I don't open up to people at all about my personal life but it felt different with this friend. I myself am an extrovert as I talk to many people but certain things about my personal life I keep to myself as well. I've never let a person affect me in such a way. One day I decided to just cut them out and its only been a few weeks but it feels like its been forever lol.
As for you stating you were shy before that was like me but over the course of the last year I've become such an outgoing and talkative person.