Why God doesn't stop satan?

[Angrboda]

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 could choose a flavor other than 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.

P1, as you've stated is that she is going to choose F at some later point. I don't care what you call them, at that point--prior to her choice--it's possible that she could choose flavor G (or any other flavor than F). But if it's possibly true that she chooses G (or any other flavor than F), then P2/P3 are possibly false--which they can't be. The only way to avoid that is if it is necessarily the case that she will choose F in the future, but if it's necessarily the case, then the choice of F isn't free. There has to be some point prior to her choice where she possibly could choose F and at which time she possibly could choose something else; that's the definition of free will. So either her choice isn't free, or P2/P3 are possibly false (a contradiction).

Is there ever a point where she could have chosen G?