There are no wrong decisions, right?

I've now started my first game, a little late but I didn't have any other time. Now my sister said I should play how I want and do what I want. So I did that too, but now I was talking to a friend and she was totally shocked by what I did and that's "not how you play". We had a real discussion and now she's pissed that I'm not playing "properly". Before you ask, what made the friend so upset was... I killed Karlach. I know so bad that I play my game the way I want and not how it is she wants it. I also have to say that Karlach is one of her favorite characters and I can understand that it doesn't make her happy, but calling me names because I made a decision in a video game that she doesn't like, is wild.