Spoilers about whodunit
I liked the red herrings that both Jumpin (black guy) and Tate also had motive and opportunity, and came in contact with the red hat.
And that she's never shown on the bus, so you really don't know for sure whodunit. She is shown knowing about the missing grate, however. And she's shown knowing how to conceal footprints (foreshadowing!)
I'm going to watch it again but isn't there a scene where she's carving a hole into the book? This is also how the hammer is hidden in the Bible on Shashank Redemption.