I doubt premeditation by a 12 year old rape victim - a victim who watched her brother murdered. The only motive I see in this case is the motive of a terrified child not wanting to be murdered at the hands of her rapist if she ‘snitched’.
What rational motive could there be for a 12 year old other than what I’ve said? Large sums of money left by her wealthy eight year old brother perhaps?
Either she was terrorized into giving a false initial statement, as now seems to be the case, or she killed her brother herself and made up a story about a rape. I don’t think the latter is the true any more but I did wonder.
And no, 12 y.o.s who kill don’t do it to inherit. They seldom have a rational motive, but they do have motives. They do it out of rage, impulse, the desire to silence the victim, psychopathy.
If they attack a stranger, you can throw in robbery and peer pressure.