Have a problem with a friend!?

Me and my friend were joking about some stuff when she told me to go to her house. I told her I was feeling lazy and she told me that it shows in my personality. She even insulted me by saying that my badminton and writing is crappy. I lashed out at her cause I'm not taking her s***. She stopped and said that I'm coming out way to strong and she'll never get used to it. But what can I do? That's just the way I am. I am defensive and that's just my nature. I'm not really a bad person (nope! never smoked, never did drugs, never drunk, never been kissed, never had a boyfriend, never had ...I'M 14 YEARS OLD) I'm not even some punk kid. I'm just defensive and I have a really strong character. NEED ADVICE PLEEEAEE!