(friends, foes, neighbors, stalkers and the "Coffee-Shop Girl") My thinking is from the way she kept looking at him ,so much so that Jenna thought she liked him. That she has has known about him for a long time.Maybe even longer than Elaine. That she really cares for him but not the way Jenna thought and that is why the strange reaction when he asked her out. I would say she actually knows him better than Elaine.