BlackWolf, patience is important and this has to be handled very carefully.
My sister, my bro-in-law & my 13 years old niece are jws. I didn't really care about my sister's belief as she's already in her middle age so she should be able to think for herself. The one i worried most is my niece. I am one of the person she look up to and we can talk about almost anything. I sometimes make fun of their religion and she can still let that go because I'm her favorite uncle. Anyway those were just small jokes. But there was once I talked a lil bit more about TTATT to her and she suddenly asked me to stop talking, and told me not to talk to her in that way in the future. I Immediately realized that this method will never work. It will only make things worse. It is important to maintain a good relationship and it is important that she will still listen to me in the future.
I also realized that even if it works and if she managed to realized TTATT, it will be very difficult for her to face it alone especially at her age. She still has to depend on her parents and the three of'em are staying so far from us(me & my family all non-jw). So I gotta switch plan.
BlackWolf, no matter what you say, don't risk breaking the good relationship between you and your sis. Make sure you guys can still talk. Lets work together. The least we can do now is try to delay her baptize. Some friends here mentioned about Jesus isn't baptized until he's 30. So imitate Jesus!