So, her mother was the actual noble.
The husband was an incompetent who married into the dukedom and he left his daughter fill out the paperwork.
And original Lunaria was smart enough to make her father an "acting duke" instead of the actual owner of the title.
She then built a strong magic power and finally, at the peak of all her political and magical power, she... committed suicide?
(Edit: an easy fix to the story would have been that the butler did the paperwork instead. Still leaves the butler as a cold individual who basically watched all this bullying unfold until his legitimate mistress decided to take action, but still a better flow than having her show cunning and willpower... then ignoring it for a weak-willed character that takes on torture for long enough to push her to suicide.)
There was also a mismatch in the flow of actions earlier, as the bell started to ring before the new Lunaria actually selected the option.
Overall, the story starts ok, but there are a few inconsistencies. I'll see how it develops, but I have mixed feelings here.