Responses
She has to prove it??? She has no evidence yet that he’s being poisoned. He’s already known as an extremely sick child.
The original "book" the child was claimed to be sick, not poisoned. The cheating queen was the heroine of the novel, so if she was poisoning the prince, that wouldn't be very heroinely. Think of it like a novel written with an unreliable narrator. So the FL doesn't know that the prince is being poisoned, she just suspects it because of the timing.
She knew the child going to be poisoned but sait nothing about it