I read in a walkthrough that I am supposed to show the riddle scroll to Dawn, and then she will tell me what the "mother's ashes" part means. According to the walkthrough, I will be given the associated item only if I have done this.
Now, my problem is, when I talked to Dawn at the wagon, I did not do this, and now when I go back to her, she simply says "come back when you have the elixir", and I am given no chance to interact with her.
Will this break the game? Can I still get the item without having Dawn decipher it?

Chances are you already did this, because Dawn doesn't react to the scroll anymore, when the riddle has already been solved by the witch doctor. (Which doctor? The witch doctor!)