Why God doesn't stop satan?

[R00tKiT]

They can't both be true in the same world, but they can be consistent with many things and they are both consistent with many possible worlds (God exists in all possible worlds).   P1 and not-P1 are not consistent with each other, but both are consistent with her having a free choice.   Free will necessarily entails that a proposition and its negation both "could be true", not that they are both true.  It simply says that both P1 and not-P1 are possible.  But if not-P1 is possible, then P2 and P3 are possibly false.  But that's not possible, because P2/P3 are necessarily true.  There's your inconsistency.  

Well I think you're misstating P1 to begin with. Here it is as I presented it in the argument :

P1 : Daughter D is going to choose flavor F of her ice cream today

which isn't the same as :

Q1 :  Daughter D could choose flavor F

P1 means that D effectively made a choice and went for F. It's not a statement about free will, it's a statement about the outcome of her free will. That's why I said P1 entails free will, but its content is more than just asserting D has free will, it gives us the result of her choice, which is flavor F.

Q1 means that D may or may not choose F, which is not the premise of my argument. So, you changed the premises of my argument....

P1       == Daughter D could choose flavor F
not-P1 == Daughter D could choose a flavor other than F

Actually your negation is false. P1 (in your formulation) entails alone that D may not go for F, that's what "could choose" means...
not-P1 would be : daughter D cannot choose flavor F, which doesn't mean she can choose other flavors, it may or may not be the case.