Timing is important. Not only does this develop character, it also ensures that two other characters will meet her at the dramatic moment when she goes back.
Complication: why does she go back?
She is unquestionably the most high-minded and noble of the characters. I was thinking she just decided to go back. Perhaps after reading a book that pricked her conscience. (She reads a lot.)
Then I remembered that I need her and the others to sneak about in fear after. Admittedly, her first two companions have good reason to sneak, but she needed a reason to not hide them and act openly herself. So --- still need a reason. Or at least, something that could happen to her on the way.