I'm no Yona expert, just read with her for the first time, but because my reading primarily addressed some upcoming choices I have before me as opposed to being predictive I asked her about free will and destiny. I don't want to state this incorrectly, and everyone should certainly feel free to ask her themselves, but the following was MY understanding of her beliefs based on how she responded to my question and an example that she gave me from her own life:
She likes tarot because it covers a short timeframe. It's predictive, so if a prediction is shown in the cards (even though it may SEEM like it's something that could be affected by a free will choice) it's either predestined or the choice has already been made at the time of the reading - either way the tarot knows which choice will ultimately be made (even though we may not feel like we've made the choice yet or even been given the choice yet). If it shows as a choice rather than a prediction, our free will still comes into play and the choice we will make is not predestined or has not yet been made and tarot won't pick an outcome up. At this point our future, with respect to that particular situation, can still be altered. That's why if she gives something AS A PREDICTION she believes it WILL happen or it would not have been shown in the cards and that's why the free will excuse cannot be made and there is no changing it. She does not believe tarot readers who have a different belief about this than her are wrong, but simply that her beliefs are based on her experience as a long-term tarot reader.
I want to reiterate that this was my interpretation of her explanation and I can't quote her without sharing her example, which I don't think is appropriate, but I believe that was the gist of what she was saying and I just wanted to share it since the question has been asked here a lot. She said she believes the big things, like who and where we meet someone are destiny, but whether we choose to involve ourselves with them for a short or long period is free will. Her point about the tarot being predictive though was that once it's shown, for the short term covered, that's what's she believes IS going to happen.