Lacey -
You have incredible advice and insight already. I will just add a little more -
Love and trust your daughter. I know you do, and it is normal to be a little fearful, when the very values and teachings that you have instilled in your daughter are being questioned.
Pray for her, that she will make the very best decision and be there for her. That's really all that is left for you to do. You have spent years teaching her values, teaching her morals, introducing her to God, and I am sure you have done a beautiful job, as I said, all that is left for you to do, is to love her, trust her and be there for her.
Sadly, this will not be the first time someone approaches your daughter and questions her faith, tries to get her to doubt her faith. It's a big huge at times wonderful at times not so wonderful world out there. There will be days filled with temptation, doubt, choices for your daughter to make. You have given her all the tools you possilbly can to allow her to make the right choice. Trust in the work and love you have given her to date.
She will be okay - trust, believe and PRAY :)