I noticed how she was checking me and my husband out all summer. When we would have an argument, she was there, generally being supportive of us, but it was a little weird. We were around each other a lot, because we live in the same area during the summer. It sounds like she was solo during your time together, so being able to observe your dynamics fascinated her. It may be awkward at first, but you can reinforce it by stopping her when she begins to state her observations about you.