Hi Mikey.
You have presented an age old problem/question - why do the evil proper, is another way of putting it. I don't know how you would feel about it - but you might want to consider reading C S Lewis' "the Problem of Pain". He deals with these issues far better than anything I could say would.
I suspect there are also Rabbis who have taken a stab at grappling with this subject. In fact, heres a link for you:
http://www.torah.org/learning/issues/badgood.htmlAnother often recommended book on the subject by a Christian author is: "When God Doesn't Make Sense" by James Dobson.
There is also a book "When bad things happen to Good People" - and I think it's author is Jewish. I'm not sure.
As for your tragic scenario - I would say the mother was wrong to promise her child any such thing. This is an idea common in some Christian groups (protection and prosperity) but it is totally un-Biblical. I do realize many a mom or dad has made such promises to a child with out really giving the matter much thought.
Still, this kind of teaching is in fact a New Age teaching, not Christian. Its the idea we create our own reality - good comes to those who expect it - who think it into being. A church teaching this may say: you'll prosper if you have faith. Speak it into being, is another idea they teach. If you want money you should say out loud: I have lots of money - and you will, is the idea. If you are ill or have hard ships, it is b./c you are harboring sin, or you do not have enough faith.
No where does the Bible say anything like this. In fact - it says quite the opposite. I'm of the opinion those who teach this are attempting to turn the All Mighty Creator, into a genie they can manipulate.
At its most extreme, as described above, I feel it is a kind of Sorcery. I believe when this kind of thing is taught in a Church, it amounts to inviting Satan into the Sanctuary.
As to the child in your scenario - My personal belief is, her confusion, fear, and pain would dissolve and disappear; and she would find herself in the company of Jesus, waiting to take her were such things never were, and never will be.
We would of corse view her death as tragic beyond words. And from our perspective, it is. No question. But I suspect, God, being eternal; and having made us with an eternal soul and destination; would not see it that way. For us, death is tragically, horribly final. But from an eternal perspective it doesn't seem that way at all.
But to be clear on another point, the one doing harm to a child is under harsh judgment. Jesus will not just stand by and let it go un noticed. He is the one about which Jesus said, he would be better off having a millstone tied around his neck, and thrown into the sea, than to face the judgment awaiting him.
Of corse, all of this is beyond the scope of the thread topic. If you want to "talk" about it some more, maybe we can go to email or PMs?