The Talk.

My sister is 15 and she is sexually active. I am 20 and I have pretty much raised her since I was 13 so we have a very close relationship. Every now and then I try and have a serious talk with her about sex and relationships covering a different topic every time so that I don't just keep saying the same thing over and over again. Tonight I want to make sure she understands that birth control does not make her invincible. I want to her to know that it does not protect her on an emotional level. I need some suggestions on how to do that without her thinking I am trying to just talk her out of it.