So confused here! To be quiet or Not???

So anyways at school, I'm kinda a quiet person. So last week, my friends were joking that when we got to 6th grade, that I could completely change, into a whole 'nother person. One that isn't quiet and stuff. I know that they were just joking, but it's bothered me ever since. I really don't wanna be that shy quiet girl anymore, and I'm willing to improve. But what will my friends say, cuz they were just joking, when they see me as a totally different person. There is also this girl at my bus stop. I wanna be friends with her (cuz we're like together at the same bus stop until high school) but we're interested in different things. What will she say when she sees me all different and new? I am really willing to cahnge, but am too afraid what other people will say, any ideas?