Is it normal to be a complete other person with every single friend?

So, a few days ago, I had quite a long talk with my mother, and the way I act with my friends. She knows that I did some bad stuff with them, whatever. Then she raised the question: "Is this what you actually do with all your friends?" Of course not, but it got me thinking, and so I told her that I actually have no duplicate on an action or feeling for another person. I am usually a pretty close-minded, and keep my problems to myself. Then my mom raised the question "Do you talk to yourself... and expect an answer?" I always do that, and actually get more than one answer. I generally use the way I act with a person to solve my problems the right way. She said that this is actually a mental disorder, and it should be treated immediately. Now my question is: Is it normal that I don;'t act the same with anyone? That I create a different personality in my mind for each and every friend? Or I am just mentally disordered as my mother sais?