If you think her work is that good, you are supposed to be impressed with making an easy fortune in short order. If someone is willing to pay millions for such work, do not deprive your daughter of such rewards for exercising her natural talents.
...or is there something missing in this equation of “childish scribble = multi million dollar painting”?
The fact that some people are willing to part with that kind of cash for childish scribble doesn't change the fact that it is still childish scribble. If people want to part with their money, that's their free choice.
I am just not going to be impressed with adults drawing childish scribble, no matter how much it is going for on the open market.