Guide her. However, expect that she will consider your advice apathetically—it's an inescapable affair. She will think that she has it all figured out and you're not one to lecture her on this matter. And then, only then when her heart is cut into ribbons will she realize that your voice was sound, only then, will she come to you for insight. That is, if she's even brave enough to talk to you about it. Be vigilant, instill sound teaching, unbendable values, and pray that our Holiness will escort her to the right man.