How do I explain free will?

Hello. My sister and I were raised Catholic but my sister has questioned and disliked the faith for a long time now. She has recently came into believing in God again but with a flawed philosophy and understanding of God. She isn’t open to listening to my arguments right now and I am not sure how to explain to her how free will is possible.

She thinks that if God knows everything that everything, every choice is known and that free will doesn’t actually exist if God knows what the choice and the result of that choice is to be. She also thinks, since having it drummed into her head ‘God is perfect’ and she feels/believes that emotions are weakness, that perfection means no emotion, in which with God being perfect, he is emotionless. And she also sees that, with unopened heart, the History of time in the Old Testament, looking only at certain examples and forgetting the good parts of it, seeing God as wrathful, that He kills off humans like that with the people in the story of Noah. And from the thinking Noah is a terrible person for enslaving his grandchild, and not looking at how God worked through Noah in other parts of his life. And she thinks that with all humans being flawed and imperfect, that even Mary sinned because she was/is also human, that there is no way that Mary could be sinless.

I know that at the moment she is not open enough and too stubborn to listen to her sister on this, but when the time comes when she will be ready where do I look to find help on what to say and explain to her how her philosophy is flawed, to get her to look at her own philosophy in a different light so she can possibly see those mistakes?

I am praying for her, always, for her conversion of heart, which only God can do. Please pray for my sister and pray that when the time comes that she is open more fully to God, that she may be open to me helping her develop her faith more fully.

Thank you and God Bless.

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Recommended Reading:
Predistination vs. Free Will

Do Catholics believe in predestination?
Is Calvinism compatible with Catholicism?
Why would God create those he knows will go to hell?

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