I am sincerely sorry for the pain your sister is going through. It's not an easy position to be in. It is best to know both sides of the situation so your sister can make the best decision for her. Each state has different laws regarding abortions. Many doctors and many states won't perform an abortion so late in the pregancy. I don't know what state or what country you are from so I cannot tell you. The baby at 5 months is already 8 to 18 inches long, and is already growing hair on his/her head and his/her internal organs are already on there way to almost being fully feveloped. If you place a stethoscope on her stomach you can hear the baby's heart beat. The baby is growing hair on his/her head and already has eyelashes, and eyebrows. Your sister may already feel the baby kicking inside. At 5 months the baby has developed a bond with the mother and now can hear and recognize her voice.
Your sister may not want the baby, but there are plenty of organizations and couples that would take the baby and raise him/her in a loving family. The baby is a part of your sister and all that is good inside her is in the child that she carries. I am sure it is very difficult for your sister to continue this pregnancy. What he did to her will never go away but can she live with herself if she decides to end her child's life as well?
I will always live with the nightmares of what happened to me 20 years ago, they never go away. But what makes it so much easier for me is knowing that I did the right thing and I stood up for my beliefs when no one would stand by myside, when no one believed me except for my Mother. I didn't know it back then but I do know it now. You can't run from yourself. The decisions you make will always be there and if you make a decision that you know you may later regret, then you are only further damaging yourself, more so than the man who raped you. 20 years later the most of my family apologized to me but the hurt and mistrust will always remain.
Your sister's baby, your niece, never did anything wrong to deserve it's life taken away. Talk to your sister and help her. If she can take something so horrendous and so ugly and turn it into something beautiful as "the gift of life", than it will only make her stronger for the battle within herself that lies before her, a life long battle.
The baby is completely innocent in all of this just like I was when it happened to me, I was only a child.
You can help your sister by contacting the local organizations and get the paperwork started. As soon as your sister gives birth, they can have the new parents waiting in the hallway ready to care for the newborn. There are a lot of couples that can't conceive and they have so much love in their hearts, that your sister's baby would be the answer to their hopes and dreams.
Hopefully this letter helps you and your sister.