Difficulties of a Dream
If Miss Linda really went through the act of poisoning her husband and having him killed, instead of being awarded the reins of the ducal family like in her dreams, the most likely outcome for her and her son would be getting pushed aside to a far away manor way off in the countryside and then be asked to live out their lives peacefully there in relative obscurity.
And this type of arrangement from the Heeat family's perspective made perfectly good sense.
After all, who in their right mind would choose to hand over the workings of their family to a nobody coming from an island a thousand miles away? Not to mention that nobody was a woman!
Just because she bore the son of their blood?
Joke!
If things were threaded so simply, the Heeat family would have long eaten from the inside from the many venomous daughter in laws they had over the centuries.