She was a great person, excellent in studies, have large amount of mana, etc. Everyone thought she's perfect to inherit the title.
But her father didn't want her to be burden with the duty of the 4 lords, and try to have multiple men from branch families be 'shared lord' to supply the mana, while she'd marry one of them, have a child to have said child (if it's male) to inherit the title instead.
Obviously, such attempt wasn't well received.
Some of the ambitious nobles even suggest 'maybe WE could supply the mana instead of the 4 lords if that's allowed'
So they let them try.
The lesser nobles could barely make a magic stone glow even with their combined magic power.
The chosen men by her father together could barely fill one.
Then she just immediately fill another empty magic stone nearby, alone, effortlessly.
Which turn the table on her father, now with everyone pushing she should succeed the title.
The father try one last attempt with asking her directly what she'd want, thinking she'd be an obedient daughter and answer with 'I'll follow my father's wish"
Nope, she chose to take on the duty AND the title.
But even after that, many still show hostility/jealousy towards her.
So the spiral began with her father's 'betrayal', then followed by the constant attempts to harass her from other jealous nobles/officers.
She's had enough, she'll make these fools regret it.
Which have some irony that she fails to notice the people who DO recognize her value.
And that she ends up being the sort of parent who doesn't 'look' at their children, just like her father.
Btw, the husband seem to be on the 'I wish you didn't choose this path, but I'll ride with you to the end wherever it goes'