I would say stay on your knees for her. Only God can change her.

As far as the child that she has born - there is not enough info to respond. Is the father caring for the child? Or has she left the child? I would have no problem reporting her to the authorities, if that's that's the case.

But she is a "prodigal daughter" in the real sense - and one day she will hit bottom and "return to her senses". When that time comes, she has to be able to come home - so don't burn any bridges. Keep the lines of communication open.

Just like any other lost person, you must be salt and light to her in the best way you can, and (back to my original statement) pray for her. In fact, ask God to do whatever it takes to bring her to brokenness. And then be ready to respond to her with love when He does that. (If she returns, do not respond to her return with judgmental words about her lifestyle -- if she is truly broken, she will be sitting in judgment on herself. At that point she will need the father to run to her with open arms, saying "This child of mine was lost, and now has come home! Put a ring on her finger and a robe on her back!")