If ever this person needed a friend it is now and that's one reason I urge you not to cut yourself off from her. Whether she realizes it or not, she will be facing enormous responsibilities in the months ahead, and she'll need others to help her so she doesn't make even more wrong decisions.
Do you remember how Jesus dealt with people who were known to have done wrong? On one occasion, a woman who had lived a very immoral life came to Him, weeping over her sins and bathing His feet with her tears. Some bystanders felt He shouldn't have anything to do with her, saying to themselves, "If this man were a prophet, he would know who is touching him and what kind of woman she is that she is a sinner" (Luke 7:39). But Jesus welcomed her, because she needed God's forgiveness and love.
And that's what your friend needs also. Yes, what she has done is wrong, and it is very serious. But be thankful she has chosen to keep this one who is growing inside her, instead of casting her child away (as so many tragically do today). The Bible urges us to "Choose life, so that you and your children may live" (Deuteronomy 30:19).
Pray for your friend, and ask God to show you ways you can help her. Most of all, encourage her to turn to Christ for the forgiveness and new life she needs.