Miracles83, it's a very good thing that you really want to help your girlfriend. In my experience (I have OCD), it's important to make her feel loved and accepted despite her symptoms. For example, if she has compulsions and she does things more and more, maybe it can be stressful also to see it, but remember that she can't control it and don't force her to stop...in my opinion. And you could ask directly to her, in a moment in which she is ok, what you could do to make her feel better in those moments. She'll be happy.
Good luck to both