This strikes me as one of those stories where there's no real happy ending. Treating others poorly, for extended periods of time, can lead to bitterness and resentment. There's a chance Mara could have grown into a perfectly normal person, hadn't it been for the way she was treated - thus creating a self-fulfilling prophecy.
On the other hand, if you're superstitious and believe in prophecies, things would have turned out bad regardless of the actions taken. Maybe she would grow into a loving family that was, unfortunately, destined to be murdered, and her desire for revenge would turn her evil. Maybe she would get kidnapped and tortured by cultists. There are many things that could happen...
Regardless, it's kind of sad to see how cruel some people can be over a superstition. Maybe we create the devils we deserve.