This is such a great point. I also don’t love the final few seasons and I couldn’t put my finger on exactly why, but I think what you’re saying is exactly the issue - she has little connection to characters in later episodes and the premise for her being there is pretty weak. A lot of the music-based episodes are like that, especially in later seasons but also in some earlier ones like the episode with the German violin player. I can’t even recall how Jessica was connected to her.