No doubt she'll be Disfellowshipped. Probably be extremely discouraged from marrying the worldy boy, or encouraged for him to become a dub. Unless she has a supportive family, she'll have a life of hell. If she is repentant after the baby is born, she'll probably be re-instated into the cogregation, if that's waht she wants.
I have seen this scenatio re-inacted many times in the over 40 years that I was a jw.
NMG