I don't think that's accurate at all. Viserys is reduced to a corpse. In reality he probably should of succumb to his disease a long time ago but kept persisting. Its not an uncommon theme for foul play to be involved when an individual has surpassed their perceived expiration date.
As for Rhaenys, they clearly forgot she was there in the first place. Hence her getting outraging and demanding an audience after being lockdown.