Frey and Robin went to the same Catholic high school. During the time they were in high school, Frey often dressed up as "Julia" to come over to Robin's dorm room. Frey and Robin are also seen comfortable together, as Robin interacts with him quite trustingly and doesn't seem to mind changing her clothes in front of him.
While Robin pretended to just be a side commentator, she was informed by Frey on who Jen was and thus conveniently commented on the graffiti artwork in front of them when she saw Jen approach, re-sparking Jen's feelings towards her artwork.
