The song Jen is singing is “Once I Was”, by the late, great Tim Buckley (father of the also late, great Jeff Buckley).

Incidentally, the first time I ever heard this song, I was listening to a rare bootleg of a cover version done by Jeff (who never really knew his father. There’s a touching story behind this performance, which you can read about at wiki). I used to be able to find Jeff’s version on Youtube, but I looked today and couldn’t find it.

If you want to hear what the song actually sounds like sung by a female voice, here’s a pretty good version.