awww thats a horrible situation for your little sis to be in, I think you are being a great big sis by offering her your support no matter what it is so important for others not to try and force or influence either way the poor thing must be feeling just terrible right now, and you are right not everyone who has a baby at a young age and does it on their own has a life of misfortune some women become stronger than ever and create a wonderful life for their little family.
I hope everything works out for her and I wish her all the luck in the world.