I'm so sorry for your loss. How lovely that you are researching for music that SHE liked! You are a wonderful daughter!
Bob Dylan - The Times They are a Changin'
Joni Mitchell - Circle Game (i like the live version from Miles of Aisles)
Bruce Springsteen - If I Should Fall Behind
The Byrds, Bob Dylan or Bruce Springsteen all have a version of "Chimes of Freedom"
Bob Dylan - Blowin' In The Wind (I like The Bootleg Series, Vol. 7"No Direction Home" version because of the harmonica stuff.
EDIT: Forgot to mention that Bruce has a good song on his Rising album "You're Missing" - nice slow rhythm.
And of course, The Byrds have the classic "Turn, Turn, Turn" -- which sings the verse from Ecclesiastes 3 in the Bible.