If your stutter doesn't bother you, you have won!!!! Don't let anyone change that! Your sister sounds incredibly insecure, don't let her infect you. Please don't let anyone affect you this much, they don't have to understand. You know what's up and that's all that matters. They can stay in thier ignorant world. My brother would try to 'help" me by saying "spit it out" and other stuff like that. But deep down they do mean well even though they really aren't helping