Soulful Survivor gave you some excellent advice. I urge you to follow this advice.
It's understandable that you feel bad about what happened to her. However, you have your own future to consider. Go to college, as you are planning to do, and get an education.
If you allow her to browbeat you into staying with her and raising this child, you will regret it. If you want to help her, make sure that she looks at the RAINN website. If she hasn't reported the rape to the police, she needs to do so. If she knows the rapist personally, she needs to file charges.
In the end, if she decides to keep this baby, then it is her responsibility to raise this child. It is NOT your obligation at all.