It's the standard 'older siblings mean to younger sibling, younger sibling wins in the end' story that's all over the world, like Cinderella from Europe or Mufaro's Beautiful Daughters from Africa. It's unclear why RFG's father lets her sisters treat her so terribly. And in Mufaro's Beautiful Daughters, at least the younger daughter gets tested on her personality, and not her weird ability to see invisible things. As usual, the younger girl gets rewarded by marrying the best guy because that's what girls want.
Message
Don't be haughty and don't lie to people? Or, make sure you can see invisible things.
