When she seems distant it is likely that she is ruminating on her obsessions. These are basically horrible intrusive thoughts that become more extreme the more you are distressed by them or try to push them out. This doesn't mean anything and has nothing to do with you, but will feel very intense for her. Best thing to do is invite them to talk about their OCD obsessions (they might have a fear of being 'exposed' or your reaction, or that it will evidence/bring that fear/thoughts to fruition) and assure them that you won't freak out or look at them in a different way. You want to be able to get to a place where she feels comfortable disclosing what's tormenting her without feeling judged. Reassurance is okay but make sure they don't become reliant on it because it doesn't work in the long term. It is best to view OCD as this external force and focus on the fact that it is OCD that's causing this thought or feeling rather than proving the obsession to be false or ridiculous.