Maybe listen to her, but don’t listen to her, if that makes sense.
You know she’s sick, and you know it’s the illness talking. So, maybe it would help you to treat her like people treat Alzheimer’s patients (because it really is a lot like that). Just go along with what she says, say a lot of things like “yes, I know”, “I’ll work on that”, “I’m sorry you feel that way”, “that’s too bad”, etc and just let it roll over you, in one ear and out the other, and don’t take it to heart.
After all, you can’t talk her out of her thoughts. Maybe, at some point, they’ll get her some medication that works, her mind will clear and you guys can enjoy your time together again.
I would, however, guard my son closely from having to hear anything like you hear. He doesn’t need that at all.