I'm not sure a 6 yr old is going to ask a lot of questions. You can introduce her as the 6 yr olds sister -- and then explain it as her Daddy is the one yr olds Daddy too, and that you are the one yr old's Mommy. I can't see the 6 yr old asking too many questions after you tell her that. Six year old children are bright, but they aren't THAT bright when it comes to sex education. And I don't think I'd introduce her as her 1/2 sister either cause that would be TOO confusing to her although you can if you'd like.

Don't confuse the issue anymore than you have to. Just tell her the truth, and take it from there. if she DOES ask some questions, answer them as truthfully as you can, but as simply as you can. It's always best to be truthful to kids, regardless of how young. Best of luck & God bless. Hugs, Lee