Theists: How can predetermined fate and free will coexist?

[Angrboda]

Let's say someone offers my kid a choice between Cake or Baked beans.  I know with as close to 100% certainty as possible, she's going to choose the Cake.  My knowledge of her future choice in cake in no way affects her freedom to choose.

So, hypothetically, if I have an omnipotent level of knowledge about her instead,  I'd likely know every choice she were about to make.  Again, my knowledge of her future choices wouldn't have anything to do with her choosing.  Her free will would remain perfectly in tact.

Your ability to predict the future choices of your daughter is unlike God's omniscience in important ways, but let's run with it. In order to have true libertarian free will, the conditions prior to your making a choice cannot 100% determine the choice you will make. If they do, then you don't have libertarian free will. She had no possibility of "having done otherwise" because her response was completely determined. So, no, her free will does not remain intact. If you actually know which choice she will make in more than a probabilistic way, then there is no possibility for her to do otherwise than you predict. She literally has no choice.