It disgusts me how this religion keeps children locked in a prison of fear and superstition. Their only thought is to escape this system and get into paradise. So many children growing up in this environment are forced to live in small isolated little worlds that prevent them from contributing to society and harnessing their innate talents for the benefit of others and for themselves.
Is your 14 year old sister baptized? If/when you leave, it seems very likely that she will zealously shun you. For the sake of your relationship with her, I'd help her little by little to expand her mind and see that not all is truth in WatchtowerLand before it's too late. If she wants to continue as a witness then that's her choice, but it would be advantageous to you if she was a "flexible" witness so that you can keep your relationship with her even if you leave.