Why should you not expect her to pay for the trasportation ? She called you to help, it was her job so she should be the one to pay. That wasn't fair at all.

And, thank God you have a good friend who understood you and decided to let go of the money.

One great lesson that I learned from this experience was never to treat any of my apprentices that way

That experience is not a good thing to replicate. Unlike the usual boss and apprentice story, where the boss would do to his/her apprentice exactly what was done to him/her in her apprentiship days.