By making a point of meeting in person, you can help fight those feelings of detachment your S. If the person you're dating feels like they have support and does not feel alienated by someone they care about you , it could help them on their journey. There may also not be a readily identifiable reason.
If you let them know that you love them, and just are there for them, you're already doing a perfect job! Maybe you don't always know what to say or how to make them feel better, maybe sometimes you don't even understand the issues they are dealing with. And if it seems like they're pushing you away, trust me, they need you more than you think.